There are little semi-translucent black stickers you can get called lightdims or something, I use those. Doesn't fully block the light but makes it very faint but still visible which I like. Sometimes you need a couple. Does not help for things like routers which have a glaring sun inside them that reflects off the white plastic and blasts out of every single ventilation hole.

The worst part is (IIRC) that blue LEDs are cheaper for the OEM, but worst in a dark room.