How do I edit model textures for Quake?

Hi.

I’m new to Quake and thought I’d try messing with mods. I decompiled a model to edit the texture, edited the texture, then recompiled it. In game, its colours were bright and different. Is there a free image editor that will make Quake-friendly textures?

Thanks,
Alex

Never mind.

I installed GIMP which works.