Bass fishing is all about confidence and concentration. The two go hand in hand. If coloring the line gives you more confidence and better concentration than its worth doing. I first saw people coloring line down on Okeechobee for flipping mats, doubt it had any affect on the bass as your really getting a reaction strike.

I use green braid for any moving baits/topwater since it is a natural color and I don't need to see it well using it for those techniques. The green color is sufficient enough for my confidence even in gin clear water when I am tied directly.

 

However, I use bright yellow for any/all bottom bait techniques because it is tremendous the advantage it provides for line watching/detecting bites. Since I am not a fan of using leaders on my pitching/flipping/heavy cover set ups I just use the line as is, but if it is bothering me, I will take a blue spike it marker to the yellow braid, making a green color. And, I use the spike it garlic markers incase the sharpie smell affects anything.

 

Most of this comes down to personal confidence, but you'd be lying to yourself if you pretend this stuff doesn't matter SOMETIMES. Like everything else in fishing: Can it matter? Yes. Does it matter? Probably not.