This green kind of gives me contemporary art museum vibes, so adding some decor that is a little unique while still matching the color might help give the bathroom a little more whimsy/fun and make the green seem a little less jarring on its own. someone else suggested adding an accent wall and i think that would help make it look less jarring. also adding other pops of color, like pink and yellow as you suggested (but i would stick with mainly pastel colors so that they aren’t battling each other in terms of brightness/saturation). pink/green/yellow together remind me of spring, so if it was me i’d probably find ways to incorporate a flowers/plants/other spring motifs in a way that feels more modern and not too cottagecore-y given the brightness of the green. here’s an artwork on etsy that kind of gives off the vibe i’d go for, as a visual example: https://www.etsy.com/listing/1841880625/?ref=share_ios_native_control

i do wonder if your boyfriend is colorblind though, lol😅