Chun-li AI Image courtesy of Methiou:
Tips for the grayscale, it would be best if the image was like a 3D render without textures, all gray like the second one here because everything you need to do next is limit the palette, add details and color separate.

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For method 2, just color separation, you cut the sections with Magic Wand and increase the Tolerance, change the color of that layer, set the palette then scale and and clean.
Method 1, Grayscale should be good for images with few details, you clean it from the get go, but is an extra step and you still have to Color Separate.
Method 2, only doing the Color Separation could be faster, but you may lose details and some random dots could pop up.
Is up to you if you want to prompt the AI image to be in Grayscale or with Color Separation.
AI would be as an alternative of tracing over the image, stylizing it, saving you time, this is a hobby after all. But you must be aware of animations, so their frames don't look jumpy and different from each other, you could focus only on keyframes and create the inbetweens or you simply fix the jumpiness.