Right now I'm using Generation InVerse - Tsutaaja. The colors are simple and easy to read with, IMO. I was previously using Johto Elite 4 for a while (Pichu^2 before that, Seeds of Platinum one before that, and Forever Standing before that :). For some reason, I just cycled through the default themes!) because the dark color looked cool, but it wasn't easy on the eyes after a while... I was going to use Generation InVerse - Zoroark for a blend of simple-to-read+dark colors, but the color scheme used for it didn't seem quite right...
So for now, Gen InVerse Tsutaaja it is! (even though I'm starting with Pokabu :D)