This is one of my own modded Game Boys. It used to have a cyan blue screen but yesterday I decided to try out a silver screen that I had recently acquired. I also tried new off-white silicon buttons. It looks great I think, though I have still not decided if I like the feeling of the new buttons.
One of the things I have found when choosing color combinations for modded Game Boys is that it usually looks better if there is a high contrast between the color of the shell and the screen. Meaning if you choose a dark shell, use a lightly colored screen and vice versa.