I bought Illustrator CS3 a while ago but hadn’t really looked into all the new features. I found a flash video from Adobe Illustrator Techniques showing the new colour features that Illustrator CS3 offers which look like they could be really useful. The first is the ability to easily change all the colours in your illustrator document using a palette showing all the colours you have you have used. These colours can easily be tweaked to try out different colour variations, you even have the option to convert a full colour job to a two colour one at the click of a button.
Another great new feature is the colour guide which lets you explore different colour combinations by providing you with various complementary colour swatches based on one of the colours you have used. This could be ideal for experimenting with colours for logo designs.
Take a look at the video for a tutorial on how to use these features.