I tried back in '05 when I was like 10 and the stickers of my Rubik's brand started to peel off.
I colored big squares of paper with felt tips, which I then cut like a 3*3 grid. I glued the paper squares with varnish glue.
Pros:
- Vibrant colors
- You'll have your own color scheme
- I did that when I was 10 so you know it's really easy to do
Cons:
- The colors started to fade about a year after
- Not sure that's WCA approved
- It's the idea of a 10 yo