Simple shader that allows for create animations similar to palette cycling. Make a grayscale sprite and a gradient, put a ShaderMaterial on the sprite and assign the gradient and it will animate. See the example project for usage.
Caveats for best effect:
- the base texture should have filter disabled
- number of colors in the gradient and base texture should match
- gray shades in the base texture should be uniformly distributed (i.e. with equal increments between colors)
Check out the repo page for animated example.