Well, first may be check your screen settings. Now emeralds is a dichroic mineral meaning that in one direction it appears bluish green (and in the other yellowish green). Dichroism is usually more visible in rough stones. Now regarding the difference between emerald and aquamarine: emeralds are colored by chromium and/or vanadium. Aquamarine on the other hand is colored by iron. Some emeralds contain a bit of iron and the color can then become a bit more bluish or a bit more yellowish. Hoping that this helped.
