Board Thread:Support Requests - Getting Technical/@comment-418817-20130128040256/@comment-188432-20130128165449

One person's "default" is another person's "crazy". You just have to play with it. I've made the default colours fit into an older colour scheme for our site — this is why I said I'm about to change it up — but you can do what you want with it. I notice you've not copied over the documentation, which would probably help you a lot at this juncture. You need to understand what it's supposed to do before you can understand how to style it. One of the big things to remember about it is that colours are modifiable by the editor, and that the colour which displays by default is not the only colour the box could have.

It's really hard to specifically advise you at this juncture, because I've no idea what the overall colour schemes of your site are.

Once you've set up your default colours and borders with the CSS, then you can move on to the collapsibility function, which is explained in some detail at mw:Manual:Collapsible elements.