Hockey, Anime, Books, Horror movies, My little pony, The walking dead, My kitties Gilly and discord.
Favorite hockey teams. Vancouver Canucks and Detroit Redwings.
Favorite players. Chris Tanev,Jonathan Toews.
You might also try listening to music without lyrics while colouring. Without lyrics is key as your brain doesn't have any silly words to latch onto and derail your attempt at relaxing.