This is a great feature idea. We currently accomplish this by setting up a "visual profile" structure of memory tags that a non-visible component in all of our windows points to (each of these "memory tags" is a custom property of the non-visible component). Then we keep database records for each possible profile to change the visual profile/theme throughout the entire designer with one action, or dynamically based on the environment. So DEV has a different color scheme from TEST and a different color scheme from PROD.

I think something like this is a better approach if you're searching to be congruent, as opposed to just having a default which you might fat-finger or forget to change. And it saves a tremendous amount of time.

It also allows us to do cool stuff like change color schemes for holiday's like halloween or 4th of July, just for a day, and everyone in the plant seems to like it.

Theme sets would be a great addition to speed initial project development by helping establish a palette for colors as well as fonts, button styles etc.

Or better yet, adopt a CSS mentality and allow for a style sheet to be applied to all screen objects in a project.