It is possible to customize the webdypro themes.Download the appropriate version of theme editor and themes you need to modify. Then down load eclipse2.1.3 and jre1.4.2 jsdk1.4.2.
Please download the exact version that i have mentioned above.Really the latest version raises errors in customization of Themes.
I have given the down load link for theme editor tool( which is a pack of jar files need to be unzipped in plug ins of eclipse workspace) and themes.
In the above link itself is a reference document which guides in customizing the SAP themes.
customize theme ,so that you can see your application in your favorite colors