Actual data about what does and does not affect resale value?

Some of the people on my HOA bylaws-rewrite committee seem to think that if one of their neighbors paints his house purple, or has a metal shed with rust on it, that this will negatively affect their own resale value. A purple house might be unusual, and a rusty shed might be unsightly or even dangerous, but I am skeptical that things like this have any significant impact on resale value.

I'd like to see some data on it. Can anyone recommend a source?