Not sure if it really matters much; except in my own psyche. I prefer to use gray, cream, olive shades only because I feel better about their subtle color. I've read about one belief that matching the colors the fish see through the surface is preferred for a camo effect, so I'm surprised I have not come across a sky blue-colored line. There may be a blue line out there, just haven't seen it. I personally get no benefit from a brighter line, so I figure why take the chance.