Quick question...Why are the arrows on some diamonds so visibly black with the naked eye and others just seem to be "clear" or like silvery mirrors while looking down on the diamond?
The arrows simply reflect what's in front of them. The color the arrows display depends on the lighting and what's in front of them, even with the same stone.
Ditto all of it. It seems most photographers, myself included, try to capture the arrows so they appear dark, which mimics how they appear in Idealscope and ASET images. In real life, they are always present in Hearts and Arrows diamonds, but it all depends on the environment which colour they look like. Hopefully yours are also beaming out every other colour too.