it's a smaller snake.. but what about some of the garters?
my personal experience is limited to one snake but
http://www.thamnophis.com/ has lots of great people and information.
Garters are active during the day, react to things outside their cages, Don't get too large, and you can keep multiples in a viv (increasing the chance that someone will be out and moving at any time) They also don't get as large as most of the snakes mentioned and have some different morphs.
You can keep more than one species together (with some exceptions)- just keep all one gender (no hybridizing) so you can have a variety.
Their husbandry varies but seems to be pretty easy and they seem to be fairly tolerant of their conditions. Their temperaments range all over, since they are prey for a lot of other things I think they run more to flighty, but many will calm down with handling.
http://i.imgur.com/Xxx3GTW.jpg
and they have blue!!
https://farm8.staticflickr.com/7328/...fce4218d_b.jpg
http://www.geckosunlimited.com/commu...oncinnus_A.JPG
https://s-media-cache-ak0.pinimg.com...28e564cc93.jpg