i dont think it has anything to do with the blue light, nor if it is on green either. the problem still persists sometimes and i've noticed it only on 2.4 so far based from all the previous versions i've been using it up until now :/
update: i noticed another issue with this 2.4 beta. although it's a minor issue there is a constant joycon and handheld mode icon of the controllers consistently popping up (not sure if it's because i have theme mode on), but if you are too also using theme mode you may noticed this issue.
here's what i have for my switch that is causing this issue i have 2 sets of joy cons it's docked, and the first set is with attached onto the switch and i am using another set free hand mode (as in, as if it i was playing the switch in table top mode... meh im so bad at explaining this but hopefully you get the idea (using it as joycons lols >.>''' while docked essentially). i don't know if this also occurs if you have your set of joycons on the switch and you're using a pro controller, as i don't have a pro controller so i wouldn't know for certain. but yeah this is another issue that i see that wasn't there on the previous versions of sx os.
edit: being a bit more specific, the pop ups icons (on the lower left corner; remember i am using theme so idk if this is happening on non theme [will test later to see]) are only seen while on menu screen of game selections etc. not while in game.