Are you primarily interested in bush or pole types? Or doesn't it matter?

You could almost pick varieties at random and get a nice cross section of colors and patterns, there are so many.

Given your small space, I would consider one of the multi-color varieites, such as Cherokee Cornfield, Sacks, and Faulkner's Cornfield. These are all pole beans which have as many as 20 different colors and patterns.
One of the prettiest beans I grow, also a pole type, is Rose. This is a largish bean. About 1/3 or so of it is a gorgeous plum color, which breaks up to speckle and frost the balance of the bean, with is an ivory color.

Snowcap and Mostoler's Wild Goose are both large beans with orange and white markings. Very pretty.

Anasazi, Thousand-Year Cave, and Trout are almost indistinguishable, with maroon and white patterns.

Etc. Etc. Etc.

If you can grow beans on a trellis, and color is the main criteria, you might consider Christmas Pole Lima. It produces very large red and white mottled seed; very striking. Take a look at the Seed Savers Exchange online catalog. You can see some pictures there. I agree heartily with Gardenlad about the Trout bean. There's no end to the possibilities.

Here is a link that might be useful: Seed Savers Exchange Catalog

I was thinking about limas and runners, but figured my post was running kind of long.

People often don't realize the diversity of colors and patterns found in the "other" beans. Take Hopi Yellow, for instance, a lima with yellow and black markings. Or some of the butterbeans, whose markings can be spectacular. Despite its bare two-tone coloring, for instance, I think Flossie Powell is gorgeous.

Thanks for the responses, guys. I have tons of beans to look into now!