Themes in SharePoint 2010 are so much better than 2007 – and so much easier to generate! You can either create them with a .thmx file from PowerPoint, or just set them up through the user interface.
One problem, though, is what areas of the page are controlled by these colours? Well, I’d been going to set up an experiment to find out, but fortunately Erik Swenson had already taken the time to map this out. So, rather than reinvent the wheel, I’ll just use that – it’s well worth a read.