Which generation of sprites are u devamping?
I'm just lining up the pokemon from platinum to the ones in crystal and pulling off the most accurate colors. For now that's working well, and if I need to I just increase or decrease the contrast to make it more accurate.
Oh for the treecko, chances are u won't be able to put in the red color. I've tried my best and it loox weird when using black, white, green, and red.