He's a really pretty turquoise.
It's pretty normal for bettas to have dark faces. Bettas that have faces the same color as their bodies are called 'masked'. Color change is pretty normal at first, but watch out for him looking pale or having horizontal streaks across his body, because that indicates stress.
Bettas can do okay in small tanks, but I'm kinda lazy so I keep mine in a 5 gal. That way I only have to do water changes 2 times a week, lol. If you go with a larger tank, make sure he has extra spaces to hide too, so he doesn't feel too exposed.
Everyone feeds a little differently, but I feed 2-3 pellets twice a day (and frozen food twice a week). When you buy pellets, make sure that the first ingredient listed is 'fish meal'. Otherwise you're buying him the betta version of potato chips, tasty, but not a lot of nutrition.
I don't know a lot about freeze dried foods, but I really like to feed frozen. My bettas have always loved brine shrimp & bloodworms in particular. It's really not that expensive. I only thaw a little bit of a block at a time, so $10 worth will last for months if you're using them 1-2 times a week. My current betta goes nuts for it.