Sorry for a late reply. I used Mesen's Palette Editor to change the sprites into a standardized jersey, shorts, skin, and hair color, and then I screenshotted to put the sprites in the sheet. It only changes the colors momentarily, however, and it goes back any time the game changes the palettes itself.

If you want to edit the game data itself to replace player colors, I wouldn't know the specifics, but using Mesens tools can help you. Mesen lets you see where in memory palettes are stored, and using the debugger and setting a breakpoint that triggers whenever one of the colors is written, you can look at the instructions that write the color into the PPU memory, find where it gets the colors, then edit it in a hex editor. If that works, the character you edited will be permanently changed, suitable for a romhack.

Hey, can someone explain how to change the colors from the sprites? I'm trying to make a TOPS Jr youth team with these sprites