yesterday (4/1/2019) my Firefox theme changed it's appearance to some sort of 80's color pallet; light blue with pink text. I usually use the Dark theme, so this color change was obvious immediately. At first I thought it was an April Fools joke but I can't find anyone in my office that has the same affect. Right away I chose a new theme from the customize menu, changing it to Dark, which worked, but only until I open a new browser window. It's so weird. See the screenshot. This happens on both Mac and Windows FF browsers that are being synced with Firefox sync.