You may get walkbacks when trying this; this is because ThingLab uses it's own custom DisplayMedium (appropriately named DisplayRegionHack) rather than Form, and it does not understand color. I am working on this at the moment.
After loading ThingLab, Monticello will not be able to manipulate the ThingLab package. I posted a bug report and a fix; file it in if you want to manipulate the ThingLab package. This is not required to run ThingLab.