Yes I did get them from this tutorial but modifed a bit cause you have to change shadows hue and highlights hue compared to middle color, otherwise its gonna look dull.
So i use color picker to pic shadows of skin, and change their color balance/hue a bit to the blue side, then change shadows of clothes etc. I think you can do multiple at once (clothes and skin with one color balance change).
Also since i use gimp a lot i had to write this down for myself to remind later, most of this is for photoshop.
https://2dwillneverdie.com/tutorial/the-making-of-el-zombo/
I scaled down in gimp using linear, you can use nearest pixel too, i also scale down only after converting to indexed 5 colours.
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Tried to colorize his grayscale sprite...
They way he did it is basic and kinda flat/dull
So i made the hue different in highlights and shadows
So red highlighted is orange and in shadow is purple
Other experiment i did with different palettes