robots.design works very well through upgrades, in this case, with dojo. Using the tundra theme, I can reskin an application - including dojo/dijit very quickly.

Some colors should not be changed - specifically error and warning displays which are traditionally red and yellow respectively. A backup of the CSS files was invaluable, since a dojo upgrade only required CSS upgrades for the dojo files (dojo.css, dijit.css, tundra.css).