I've released a new tutorial on my website covering the basics of colorizing an image with the Colorize Tool! You can find the tutorial here: https://feniksdev.com/how-to-colorize-images-in-renpy/

And you can pick up the Colorize Tool here if you haven't tried it yet:

Even if you don't have something like character customization in your current game, I encourage you to take a look at the tool to see if it'd be a good fit for a future project. Colorizing images in-engine can help with other things besides just character customization - you can recolour things like items, animals, or cut-in images to get more variety out of them, or even consider mixing and matching recoloured NPC parts to get more mileage out of side character sprites. You can use this shader on UI elements also, or for minigames. There are lots of possibilities!

I've got a few more tutorials planned to go over the tool and shader that I'll be releasing in the coming weeks as well; roughly, the drafted ones are:

1. How to separate and format images for recolouring
2. How to use the RGB colour sets to get even more depth out of your base images and section off areas (e.g. for eyes, mouths) (this one might be two parts honestly)
3. How to create images from scratch for the shader - this one is aimed at artists rather than non-artists adapting existing art for the tool

I'd love to hear which topics you think I should post first!