Arboreal, but small

Not brightly colored but Indonesian tree boas would fit your requirements

Do you have any info on the handling of these Indonesian tree boas? They are very interesting and quite small.

I have no personal experience with them but here's a good read about the different types http://www.herpnation.com/hn-blog/ca...=chris-carille

I keep Pacific Tree Boas. My suggestion would be something like Indonesian Tree Boas Candoia Corinata. They are relatively inexpensive , are completely docile, not at all shy, have a very slow metabolism so they only need to eat every 2-3 weeks, and come in a variety of colors and patterns. Males only get up to about 2 feet whole the females are usually in the 30-36 inch range.