Is blue the only color for fluorescence?

Blue is not the only colour of fluorescence - it is merely the most common colour. "Medium" or "Faint" or "Stong" indicates the strength of fluorescence.

See the link below for a GIA study on fluorescence which explains more about fluorescence.
http://lgdl.gia.edu/pdfs/W97_fluoresce.pdf 

Here is a summary from that study
"Some gem diamonds fluoresce, most commonly blue, to the concentrated long-wave ultraviolet radiation of a UV lamp. There is a perception in the trade that this fluorescence has a negative effect on the overall appearance of such a diamond. Visual observation experiments were conducted to study this relationship. Four sets of very similar round brilliant diamonds, covering the color range from colorless to faint yellow, were selected for the different commonly encountered strengths of blue fluorescence they represented. These diamonds were then observed by trained graders, trade professionals, and average observers in various stone positions and lighting environments. For the average observer, meant to represent the jewelry buying public, no systematic effects of fluorescence were detected. Even the experienced observers did not consistently agree on the effects of fluorescence from one stone to the next. In general, the results revealed that strongly blue fluorescent diamonds were perceived to have a better color appearance when viewed table-up, with no discernible trend table-down. Most observers saw no relationship between fluorescence and transparency."

For those who like to know details - here is more details about what causes the different colours!

"Gem diamonds typically contain a variety of structural
defects, most involving impurity atoms such as
nitrogen, hydrogen, and boron. Nitrogen-related defects
are the most common of these, and only some of the
resulting defects cause luminescence (Clark et al.,
1992; Collins, 1992; see also Davies et al., 1978). The
nitrogen-related defects, and their association with fluorescence,
are described as follows:
• A single nitrogen atom substituting for carbon in a
diamond that is partly type Ib (see, e.g., Fritsch and
Scarratt, 1992) produces orangy yellow fluorescence.
• A group of two nitrogen atoms, the A aggregate, tends
to quench—that is, extinguish—fluorescence.
• A group of three nitrogen atoms is called the N3 center,
and produces blue fluorescence.
• A group of four nitrogen atoms is called the B aggregate,
and is not known to cause luminescence.
• A lens-shaped cluster of nitrogen atoms is called a
platelet, and is associated with yellow fluorescence.
• A single nitrogen atom trapped near a carbon vacancy
causes bright orange fluorescence.
• A vacancy trapped near an A or B aggregate is called
the H3 (H4) center, and generates green fluorescence.

A single diamond may contain several different
kinds of defects, leading to a range of complex relationships
between nitrogen content, nitrogen aggregation
state, diamond color, and fluorescence color and
strength. A diamond may also display two different fluorescence
colors, either clearly zoned or closely mixed
together. As described in the Background section of the
text, of 5,710 colorless to near-colorless diamonds that
fluoresced a noticeable color, 97% showed blue fluorescence,
which is caused by the N3 center. Of 16,835 diamonds
in the same study that did not fluoresce, many
contained N3 centers, but they also contained enough
A aggregates to prevent any visible luminescence. The
existence of N3 centers in these diamonds is suggested
by their yellow bodycolor (most commonly caused by
“Cape” absorption bands, which are related to these
centers); the existence of A aggregates (or other centers
that quench luminescence) is evident from the fact that
the stones do not fluoresce. These complexities confound
the trade notion that nonfluorescent
diamonds are more “pure” than those that
fluoresce, since there are nitrogen-related
centers that extinguish fluorescence, as
well as those that cause blue fluorescence

Dr. Indira Marchant
The Royal Exchange
Best Diamonds

"You just never know what tomorrow will bring!"

Wink Jones
GG
Winfield's/High Performance Diamonds

Wink Jones
GG
Winfield's/High Performance Diamonds

Dr. Indira Marchant
The Royal Exchange
Best Diamonds

"You just never know what tomorrow will bring!"

Garry Holloway FGAA DipDT

HCA and Ideal-scope developer

http://www.ideal-scope.com and
http://www.HollowayDiamonds.com.au

"You just never know what tomorrow will bring!"

****** Life is a Journey, not a Destination. ******

"You just never know what tomorrow will bring!"

"You just never know what tomorrow will bring!"

Coati, G.G.

"You just never know what tomorrow will bring!"

Coati, G.G.

Date: 8/1/2008 5:18:44 PM
Author: ButterBean
Flygirl, that's wonderful! Your little green pear is positively JUICY! Makes me think there may be one with my name on it down the road. But first ... Could I ask for more pics of your Ering stone, too? I would love to see what the medium blue looks like in all different lighting ... please? I do believe that mb is for me.
Thanks! BB

****** Life is a Journey, not a Destination. ******

Gary

www.diamondexpert.com

"You just never know what tomorrow will bring!"

~~~~~~~~~~~~~~~~

"It is also important for the State to inculcate in its subjects an aversion to any 'conspiracy theory of history' for a search for 'conspiracies' means a search for motives and an attribution of responsibility for historical misdeeds."

-Murray N. Rothbard, in The Anatomy of the State



John Swinton [1829-1901] Chief Editorial Writer of the New York Times (Considered "the Dean of his Profession" by his peers), when asked to toast an 'Independent Press' in a gathering at the National Press Club, circa 1880

"There is no such thing in America as an independent press unless it is in the country towns. You know it, and I know it. There is not one of you who dare express an honest opinion. If you express it you know beforehand that it would never appear in print. I am paid... for keeping my honest opinions out of the paper I am connected with. Others of you are paid similar salaries for doing similar things....

The business of the New York journalist is to distort the truth, to lie outright, to pervert, to vilify, to fawn at the feet of Mammon, and sell his country and race for his daily bread, or for what is about the same thing, his salary. You know this, and I know it and what foolery to be toasting an 'independent press.' We are tools, and the vassals of rich men behind the scenes. We are jumping-jacks. They pull the strings and we dance. Our time, our talents, our lives, our possibilities, all are the property of other men. We are intellectual prostitutes."

~~~~~~~~~~~~~~~~

"It is also important for the State to inculcate in its subjects an aversion to any 'conspiracy theory of history' for a search for 'conspiracies' means a search for motives and an attribution of responsibility for historical misdeeds."

-Murray N. Rothbard, in The Anatomy of the State



John Swinton [1829-1901] Chief Editorial Writer of the New York Times (Considered "the Dean of his Profession" by his peers), when asked to toast an 'Independent Press' in a gathering at the National Press Club, circa 1880

"There is no such thing in America as an independent press unless it is in the country towns. You know it, and I know it. There is not one of you who dare express an honest opinion. If you express it you know beforehand that it would never appear in print. I am paid... for keeping my honest opinions out of the paper I am connected with. Others of you are paid similar salaries for doing similar things....

The business of the New York journalist is to distort the truth, to lie outright, to pervert, to vilify, to fawn at the feet of Mammon, and sell his country and race for his daily bread, or for what is about the same thing, his salary. You know this, and I know it and what foolery to be toasting an 'independent press.' We are tools, and the vassals of rich men behind the scenes. We are jumping-jacks. They pull the strings and we dance. Our time, our talents, our lives, our possibilities, all are the property of other men. We are intellectual prostitutes."

~~~~~~~~~~~~~~~~

"It is also important for the State to inculcate in its subjects an aversion to any 'conspiracy theory of history' for a search for 'conspiracies' means a search for motives and an attribution of responsibility for historical misdeeds."

-Murray N. Rothbard, in The Anatomy of the State



John Swinton [1829-1901] Chief Editorial Writer of the New York Times (Considered "the Dean of his Profession" by his peers), when asked to toast an 'Independent Press' in a gathering at the National Press Club, circa 1880

"There is no such thing in America as an independent press unless it is in the country towns. You know it, and I know it. There is not one of you who dare express an honest opinion. If you express it you know beforehand that it would never appear in print. I am paid... for keeping my honest opinions out of the paper I am connected with. Others of you are paid similar salaries for doing similar things....

The business of the New York journalist is to distort the truth, to lie outright, to pervert, to vilify, to fawn at the feet of Mammon, and sell his country and race for his daily bread, or for what is about the same thing, his salary. You know this, and I know it and what foolery to be toasting an 'independent press.' We are tools, and the vassals of rich men behind the scenes. We are jumping-jacks. They pull the strings and we dance. Our time, our talents, our lives, our possibilities, all are the property of other men. We are intellectual prostitutes."

~~~~~~~~~~~~~~~~

"It is also important for the State to inculcate in its subjects an aversion to any 'conspiracy theory of history' for a search for 'conspiracies' means a search for motives and an attribution of responsibility for historical misdeeds."

-Murray N. Rothbard, in The Anatomy of the State



John Swinton [1829-1901] Chief Editorial Writer of the New York Times (Considered "the Dean of his Profession" by his peers), when asked to toast an 'Independent Press' in a gathering at the National Press Club, circa 1880

"There is no such thing in America as an independent press unless it is in the country towns. You know it, and I know it. There is not one of you who dare express an honest opinion. If you express it you know beforehand that it would never appear in print. I am paid... for keeping my honest opinions out of the paper I am connected with. Others of you are paid similar salaries for doing similar things....

The business of the New York journalist is to distort the truth, to lie outright, to pervert, to vilify, to fawn at the feet of Mammon, and sell his country and race for his daily bread, or for what is about the same thing, his salary. You know this, and I know it and what foolery to be toasting an 'independent press.' We are tools, and the vassals of rich men behind the scenes. We are jumping-jacks. They pull the strings and we dance. Our time, our talents, our lives, our possibilities, all are the property of other men. We are intellectual prostitutes."