Ok, I've finished making a quick sort of thing. Turned out not looking very much like the rtp unfortunately, but I hope it's of some kind of use anyway.
Link
There are a few options each for body shape, beak, eyes, crest and background. To use, open in photoshop or clip studio paint, and make visible the folders of the features you want. For the most part, you'll not want to mess with the visibility of individual layers. To recolour a feature, just fill in the clipping layers with a colour.
It'll probably benefit from you adding your own feather patterns, extra shading etc; I wanted to put some in, but struggled to make it fit all 3 body types. Feel free to edit and use however you like, tracing's fine too. Just don't take out the backgrounds and use them for other things.
Example:
