I have started using Trello.com for task management, but I really want to be able to customize the colors on different boards.
Is there any way to do this? Is it a possibility now or a possible future enhancement?
I don't believe that this is possible, with functionality currently built in to Trello.
However, the Trello Development Board (on Trello, of course), is useful to see what features are being talked about, and to vote for your favourite features.
They have a card for that actually, you can go there and vote it up
You can now change the colour of the background from that blue to other colours:
Menu → Settings → Change Background...
You can at first select among six colours, but if you want to use some other patterns, a photo background or your own image, you will have to upgrade to Trello Gold.
With Trello Gold, you can choose from nine stunning, hand-picked backgrounds, or upload your own. With custom backgrounds, the image goes edge to edge and the header and lists will go slightly transparent so your background really shines.
Some updated links - my Chrome extension for setting custom Trello background colors. Hope it does what you need.
On the Chrome web store: http://chrome.google.com/webstore/detail/ppmoihbfiilgkkgcogbblhhanjjaocil
An explanatory blog post: http://thoughts.mindofmoses.com/read/customize-your-trello-boards-with-beautify