You will probably never notice a difference with your eye. The eternity band will be (presumably) made with fldimaonds much smaller than that in your solitaire. Generally smaller stones, because their mass is less, won't appear as tinted as larger (not like D or E have any discernible tint). Just make sure they are well cut stones.
Unless you are extremely color sensitive, you could easily pair your E solitaire up with melee diamonds as low as H-I that are well cut and not notice the color difference. Pairing your solitaire E up with D-E is going to be perfect!
Often times the overall design will change recommendations for this slightly - do you have photos of the rings?
Some designs. for instance, actually work well with a center stone with more color than the surrounding melee.
Either way, your D/E eternity band should be fantastic paired with an E center stone (provided the same lab (or labs with similar standards) is/are grading the diamonds)
I mean the vendor feels the diamonds look the same enough to pair them together (d/e) and you have on of the colors in that pair (e) seems like a non issue.
HI April,
Welcome to PS!
It's likely that your solitaire is graded by a lab ( GIA hopefully)
Also most likely the eternity band is not.
If my assumptions are correct, there may be a difference in color if all were graded by GIA.
But as Wink says, it's unlikely you'd be able to notice a difference, even if the D-E is not graded as strictly as the E