What colour walls - 13 year old?

Well if you're decorating his room them its best to match things together, but on the other hand if you know he has an obsession for something them get some sets for it. Looking at the bed you've ordered i would choose a range of blue's try them out and see which one is best, but be warned don't use the same colour as the bed otherwise it will look to plain and dull. I personally would choose something a little darker than turquoise. And you might like to find some other BENCH stuff as-well.