Colour of lines is determined by the type of line.
For example, Nylon is available in white, green and red. Dacron is available in white (natural) or red. At one point, Basic Research lined a few BASE canopies with black Dacron, but that is really rare.
Kevlar is only available in yellow
Spectra is only available in white.
Vectran is only available in yellow.
HMA is available in yellow or black. The black HMA is only available from HiPer USA. The black is a UV inhibitor, molded into the fibers early in the process.
Hi Billy, I think it is not a matter of which material is better but which one suits you and your canopy better. Generally speaking the most common options are: Microline – lasts longer, has low bulk and low drag but changes dimensions considerably and does not absorb the shock (such as in a hard opening); Dacron – can absorb part of the shock in a hard opening which may save your neck (I have no idea of how it changes trim as you jump), increases pack volume and drag; Vectran – stay in trim for the lifespan of the lineset, has low bulk and low drag but does not absorb shock and has a shorter lifespan than Microline. Your best bet should be stay with the original material according to manufacturer specs. They have designed the canopy taking the material properties in consideration so it is most certainly appropriate. Personally I prefer Vectran because I like the idea of keeping the performance and opening characteristics unchanged through the life of the canopy. If you decide to change materials, make sure they are compatible with your system. For example, some manufacturers use a modified trim chart for Microline that includes some “errors” to compensate for line shrinkage and/or elongation. This way the canopy reaches the perfect trim only after a certain number of jumps. If you decide to build a lineset with Vectran based on this chart you’ll get a canopy that is out of the ideal trim from first to the last jump. Vectran requires also stainless steel grommets for the slider as it is extremely abrasive to brass. I think you can get Dacron at least in red and white but I’m almost sure there are no color options for Microline and Vectran. BTW, I’m neither a rigger nor experienced skydiver, just a mechanical engineer who tries to understand as much as possible about gear by reading a lot. There are a lot of very experienced people here that can add a lot more and correct any misinformation that I may have said.