My latest project is tidying up a Joomla! CMS web site that was built using Artiseer. This is (proprietary) software designed to easily generate templates for Drupal and Joomla! amongst others. It looks interesting (apart from the sexist twaddle on the home page), although the CSS it spits out looks like it's been spat out.
Part of the project is the integration of the Free Software phpBB3 forum with Joomla!. There's a magnificent and mightily configurable 'bridge' extension for Joomla! called JFusion. This enables you to login once in Joomla! and then be automatically logged in to the forum.
Linking to the forum from the main menu was easy enough as well -- Jooomla!'s Wrapper menu type inserts an iframe in the body of the content. This saved me hours of rebuilding the header and footer to fit a standalone forum.
The final task was to reskin the forum in the corporate colours. The default theme (prosilver) worked layout-wise but it's predominantly blue, and my client's corporate colour is predominantly red. I found a lemonpeasy way to rework the style sheet, which is handily called color.css.
Using Geany, my favouritest Linux GUI text editor, I highlighted the original blue colour in the stylesheet and opened the colour chooser dialog. I then spun the colour wheel to the same hue as the red used by my client (in this case 340). Copy the new [hex colour value], cancel the colour chooser dialog, and a quick search and replace for the original blue.
I used essentially the same technique for changing the icons -- open up the GIFs in GNU IMP, convert to RGB, go to Colours > Colourise..., change the hue to 340, convert to index, save and close.
All nice and easy, all with Free Software. Hope this can help others in the same reskinning boat!