Hi qmc, the MoI UI is made up of various .htm .css and image files that you can find in the ui subfolder. It can be customized by editing those various files. htm and css files are text files that you edit with a text editor program.

But an easier way to start out with just changing colors only is Chipp's tool here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7245.1

- Michael