Nevermind, I figured out how to do it. I just opened the block files in:
/styles/prosilver/template/portal/block/

and colours.css in
/styles/prosilver/theme/

and created a new class and then used the class in the block files in the appropiate places.

Your Portal Version: 1.0.5
Your phpBB Type: Standard phpBB3
MODs installed: Yes
Your knowledge: Basic Knowledge
Boardlink: http://sofablend.com

PHP Version: 5.2.13
MySQL Version: 5.1.47

What have you done before the problem was there?
I installed Board3 Portal.

What have you already ...