Why recolour by ramps
A good sprite does not use one red for a cloak. It uses a dark red for the shadow, a mid red and a light red for the highlight, sometimes shifting towards purple in the shadows and orange in the light. Swapping one colour at a time breaks that, and a hue slider on the whole image turns the skin and the eyes too. This tool sorts the colours into ramps, so you repaint the cloak as one thing and every step of its shading moves together.
Variants for enemies, teams and skins
Make a variant for each enemy tier, each team or each rare skin. Lock the ramps that should never change, such as skin and outline, and press Random to roll new combinations. Sprite sheets work the same way, since every frame uses the same colours.
Palette swap at runtime
For pixel art with up to 256 exact colours, Pro gives you two small palette textures and a shader for Godot 4 and Unity. Ship one sprite sheet and switch the variant with a single number, which saves memory and lets players pick colours. Painted sprites have too many colours for that, so use the baked variant PNGs instead.
Is my sprite uploaded?
No. Everything happens in your browser.