The one you posted in the thread. When I try and color a shade of the backsprite, it only colors 1 pixel, which leads me to infer that it was as jpg or gif or something. Either that, or you used a bad source for the original sprite, such as Bulbapedia.
Don't worry about it. They shouldn't be in a different format.... Let me go back and look.
Edit: I'm looking and the outlining looks really crappy around the head fin, however, I don't see any color issues or things that wouldn't let you recolor. I used the same method for every sprite, so idk. Which sheet are you using?
Alright. Also did you save the Mudkip sprites in a different file format or something? The way the colors are distributed are really strange, and I can't recolor it. (not trying to sound like a dick, your contributions are much appreciated)
So I just noticed on your Marshtomp front sprite that you changed a lot of the black outlines to color outlines. For future reference, I would prefer if you not do this because it doesn't necessarily make the sprite look better in my opinion, and it gives me more work to do because then I have to change it back.
Haha yeah. You see, before it just got annoying for me to keep track of every non-Unova contribution someone made, and people would pester me like "hey didz u seez my sprites" when I'm trying to get the Unova sprites done lol. Now that the Unova sprites are actually almost done (arguably the hardest sprites to do since all 156 Unova Pokemon required custom backsprites), its not so much of a problem for me to keep track of contributions anymore. And this will also let the project be finished faster
(but with quality still assured!)