I would LOVE to see this. I use Evernote for a lot of different things, but one of the things I started using it for several years back is for journaling. When I want to jot down some thoughts for the day, I'd love to be able to change the page color. I'm a Premium User, and I'd love to see it added as an option. And I am almost exclusively using it on mobile (Android), so app support would be highly desired!!