An artist friend of mine has some super cool “coloring book” pages he’s been using with summer campers for years… it struck me that this would make a great coloring book. How do you get something like that published? Trying to help him out 
don’t know this market, but self publishing may be the best option, specific tips on colouring books here:
https://www.youtube.com/watch?v=HHRmsIiMVmU
good luck to your friend
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