The theme is using its "Private browser" theme for the regular window. Its not the bright colours but the darker one. Annoying as I can't quickly differentiate between the two windows. I have tried refreshing the browser already and no difference.

Installing this addon creates a copy called "Firefox Radiance" which looks the same with a slight difference in the tab colour.

Finally I can see the active tab.
It actually installs two versions, very similar to each other.
One is "firefox alpenglow", and the other is "firefox radiance" which is my favorite.

the best firefox theme