There are two options to build themes using following tools
At first look above tools look very easy to create themes but there are lot limitations and not well defined
- You can only change colors.
- You can not change design elements.
Themes in SharePoint 2010 are pretty tough. There are about 60 permutations, and you can only define about 10 of those colors.
- Here is a very useful article for developers which is well explained about how to build themes.
http://eschrader.com/2010/09/23/sharepoint-2010-%E2%80%93-themes-and-corev4-css-comparison-technique-for-developers/ - Another article explains about basic permutations
https://www.nothingbutsharepoint.com/sites/eusp/Pages/custom-themes-in-sharepoint-foundation-2010.aspx
Happy Customization!
