You can use the same script to provide you diferent color/images layouts for diferent domains.
1- you build your core script, working upon a certain CSS file structure, then you create as many different CSS files as you wish
2 - At the DNS Server you point all the desired domains to the same webfolder/script
3 - At your script, you retrieve the domain your user asked for using $_SERVER[HTTP_HOST]
3 - Using the IF conditional structure your script chooses the desired CSS file to use acording with the requested domain.
The only CMS I am familiar with is the one I have created and own, but I guess you can easely do the same with Joomla, Mambo, Wordpress or any other you wish.
If you dont want to waste time doing it, I can easely have it working for you at datagen.eu , but obviously not for free.