Looks like Anniversary update changed something significant.
Before anniversary I were getting white windows with no theme atlas.
With 1.5, I am always getting colored title bars now, no matter if the "Show color in Titlebar" is checked or not. Looks like I cannot turn off coloring of titlebars now, and I really like the old UI I've got.
There are the screenshots before anniversary update and after it with 1.5 stable.