Okay, I FINALLY figured out how to do this! Go to the Personalization screen. Choose one of the High Contrast Themes. When that screen displays, it will allow you to change the colors of your desktop, buttons, title bars, etc. You may have to play with the colors a little to get what you want, but I personally am thrilled to get away from the ghost of White/Gray or Dark Gray themes. Now I don't get headaches from the glare!
Hope this helps. Funny the Microsoft IT person couldn't figure this out - and only replied those white/gray themes were "by design". LOL.