But green isn't going to work, especially for any guy I know. [...] they are polarizingly bright, and most of them are quite feminine
Objective and anecdotal. I can easily counter by saying I'm male, and own a green 5c, and assert that it isn't "hideous." Furthermore I can assert that most of the colors are actually gender neutral. Even the "pink" is more of a coral color. Color alone isn't going to doom the 5c, and I know a lot of people who are actually considering the 5c simply
because they want a color choice.
The resellability for the 5c right now isn't particularly because of color either. I'd hazard a guess that most
Swappa users are not in the color liking demographic. That doesn't represent a larger and more varied population. Furthermore, they're probably going to buy a better specced Android device in a similar price range. Taking it to Ebay or Craigslist could yield different results. Also, the likeliness of reselling it will probably increase as 5s furor dies down.
Looking at the green 5c listings, Sprint's seem to make up the glut. Can you blame them? Everyone I know on Sprint isn't exactly happy with their service... (oops, an anecdote of my own!) EDIT: The blue AT&T one is pretty clogged up too. Might be too early to infer anything still.