Did somebody in Duolingo's design department...
...look at a bag of plastic Easter eggs and think "OMG! These colors! So beautiful, so bright, must use for new update!"? In fact, some of the new skills in my Spanish tree have a picture of an egg with green dots. Coincidence?
Yeah, I logged into Duolingo this morning only to suffer immediate pain to my eyes, especially the neon yellow of the completed skills. I suppose I'll get used to it, but I'm hoping this is just temporary and you'll go back to more tolerable colors.