olive_juice, oh... it's really him! what a shame... I've never heard about this movie before

I MUST see it!!
Kimby, thank you! I used regular spray paints. Although I haven't washed the shirt yet and I can't say for sure how the colors will behave. I used regular acrylics on shirts before, but they weren't spray paints, I had to use a brush for them. However, they survived even after the washmachine!

As for the gradual fade, first I sprayed about 3/4 of the image with blue, for the last part I used a thinner layer of paint as in the beginning. Then I started to spray with purple from the other side and also used a thinner layer in the part where purple overlapped the blue part.
nataluna, thank you for the great idea with the speech balloon! I haven't even thought about it! In this particular case it doesn't bother me a lot because it was a kind of test piece (although I'm wearing it now for several days

), but I have some similar shirts that I'd like to use in the future so I think I could use your idea there!!!