I tried having a look around the styles options on my board, but I was a bit overthrown by all the options! Is there an easy guide knocking around on what changes what? Failing that, how easy/difficult would it be to replicate the colour of this site?
It's fairly straightforward, I suggest you start in the Admin area and go to Appearance / Style Properties.
Then you can click on each part of the site you want to change, most are pretty clear, if you get stuck, ask here.
So for example, to change page background to yellow, go to General / HTML and pick a new background colour.
The good thing is if you make a mistake you can reset it back to the original value, so there is a lot to be gained here by experimenting, as you work through the options, do some changes to them all, see what happens (have the forum open in another window so you can refresh the page and see your changes as you go along).
I think XenFans did some video tutorials too which ran through the main options.