The color is up to you. As far as I know, the color won't affect the ease or difficulty of care. It totally depends on if your a color morph person or not. Or if you don't mind spending the extra money for a pink morph.
The care of these guys is pretty straight forward in my mind. First off, plan on this thing growing into a big turtle. A quarter size baby will grow to a 100 pound animal over the course of its life. It's life being a 60, 70, and 80 or more years. And they will try to bite you whenever lifted from the water. Mine has out grown at least 3 tanks since I've gotten it. When I first got mine, I kept him in a 10 gallon tank until he out grew that, and kept moving him into tanks that suited his size. Right now I house him in a 55 gallon and, since he has about a 8 inch carapace length currently, he's gotten to the point where he's (once again) out grown the tank, so I'm going to move him into an "indoor pond" setup as soon as Winter Break starts for me.
Keep the temperature around 80 or so degrees, that should keep problems like lack of appetite out of the way. And these are not "basking turtles", in fact, they never leave the water (except for females when laying eggs). They are a 100% aquatic, so a submersible heater is what I suggest (and what I use). At first I thought the turtle might bite at it and hurt himself, but so far I have observed no such behavior. I keep mine on large gravel, but that is up to you. You can keep the bottom bare or add gravel or whatever. Get a good filter too, unless your planning on frequent water changes. A good filter is worth the money especially if you don't want to change the water every couple days.
These turtles like to hide (actually LOVE to hide), so provide some kind of hide spot (like a piece of driftwood), just something they can get under or in between and still be able to reach the surface to breath. Oh, and that's another thing. Don't keep the water level to high, even though these turtles are 100% aquatic, they don't swim well (strange I know) and may even drown if kept in water that's too deep. Keep the water as high as the turtle can stretch it's neck to reach the surface... if that makes sense.
As for diet, I've fed mine all kinds of turtle pellets, live feeder fish, dead fish used for fishing bait, mice, and snails. As babies, they really like turtle pellets (atleast mine did) and LIVE feeder fish like guppies or rosies. DO NOT get goldfish, I don't trust them since they carry a lot of bad stuff that could hurt your pet. By getting live fish, you can observe the "angling" action the Alligator Snapper is famous for. Believe me, it is cool. I still get excited watching my turtle dangle his fleshy worm-like lure to any passing fish. As the turtle gets older, you should offer larger food items. Mine is currently feeding on larger bait fish like finger mullet. I've heard of adults being fed large dead fish, chicken and turkey parts, large rats, and things of that nature. Feed them whenever they seem hungry. I'm not sure if everyone would agree with that, but that's how I've been doing it and my turtle is happy.
If you plan on handling the turtle a lot, I'd suggest you don't. They do not like it. It stresses them. They feel vulnerable out of water and will gape at you and, if close enough, snap at any body part it can reach. Of course, you'll occasionally have to move your turtle from point A to point B, but as for excessive handling that's just not a good idea.
Did I miss anything? If I did I'm sure one of the other snapper guys on the forum will spot it for me. Good luck.