I saw a video review for switch docks, and the guy on those videos had half neon blue and half gray. Although I feel like he only paid for the front shell rather than a full shell, because it didn't look that great. (but you aren't looking at the back when playing so I suppose it's cheaper if you don't care)
I bought a grey switch set with neon green replacement shells, but if I got the neon set I could have mixed the shells from the neon red, blue and green. That might have looked neat to have 3 colours on each joycon if that's your sort of thing.