Hi!
I think it'd be cool if there was different textures for different colors. E.G. Blue = up and down (maybe puffy paint?) Although puffy paint is black, I'm pretty sure.
I used to do art classes because I enjoyed it a lot, and my teachers came up with creative ways to help me with actually doing art. What about glitter paint, too? The glitter could be felt.
You could also look into this product called a Tact Sketch Pad to help you out a bit. Here is the
$1 to look at if you'd like.
I hope my input helps you out!