Couldn't find any info on this in the forum so I thought I'd post about it.
The desktop app seems to sometimes grey out various buttons, specifically the left sidebar buttons. It's so far happened a couple times since the update. It doesn't break any functionality from what I've seen, but it's very strange.
Using Spotify Premium, Win10, Nvidia graphics latest drivers etc
Last time it happened it fixed itself from just clicking around a bit, but as I'm writing this it hasn't gone back despite doing similar clicking.
In my screenshot "Your Library" is the only text not greyed out, there doesn't appear to be a specific reason for that. It doesn't change if I stay on another button, either hovering or clicking.
I've attached 1 screenshot without selecting anything, the 2nd where I've selected one of the greyed out bars.