Depending on what type of snake you want, and how much you care/are willing to spend on its genetics, yes you can.
Kinda like dogs and cats, there are specific breeders for almost every kinda snake you can think of, but there are also plenty available through petsmart/petco and mom&pop pet stores. Both of mine were from petco originally, but the other species I mentioned would have to be through a breeder or specialty reptile shop.
When you buy reptiles from the big names, you don't really know how they were bred or cared for, and there is generally more "risk" involved, in the looks department especially. A lot of baby snakes look nothing like what they will grow up to be, so it's a bit of a crap-shoot anyways.
With breeders, you can get specific variations, or morphs, and usually pics are posted of the exact snake up for sale, with length and weight info and hatch date to boot. The price reflects the difference though. For example, my Rainbow Boa would be $150 as a baby from Petco, and I got her on sale for $75. From a breeder online, I could have gotten the exact snake that I wanted, but it woulda been $300 BEFORE shipping, which isn't cheap for live animals.
I happen to live not more than a half hour from this place called New England Reptile Distributors, NERD, which is actually one of the larger breeding operations in the country, and they have just about every kinda snake I could wish for. I go there just to play with snakes a couple times a month.
Edit:
Also, it's worth noting that when I got this boa from Petco she was kept in an environment far too dry, and was very pale/dull in color. A few weeks of being in the vivarium with proper humidity and good soil to hide in, and she was practically glowing. People who worked at the store couldn't believe the pictures. Just goes to show that the care given can have a huge effect on appearance.