As I said earlier, I agree it probably rarely matters.
But I don't see the advantage of the crazy bright colors either. Does anyone actually struggle to see their fly line? I'm used to using muted colors for all outdoor pursuits. Sometimes camo, but earth tone browns, greens, etc. are fine. You don't wear bright orange or blue shirts when on stream. Waders are usually on the rock colored spectrum, which makes sense to me, you don't see chartreuse for a reason, there's no advantage to it. Would there be a disadvantage? Sometimes, maybe, err, I dunno, but why take the chance?
I don't see any drawback to using the muted colors. I've always been a little perplexed to why lines are made with bright colors at all. Moss green and other earth tones seem to be the exception, but I can't figure out whey they even make anything else?