Marlow ins Marstron is an 8-plait, continuous-filament Polypropylene that is lightweight, flexible, easy to coil, and soft to handle. It also floats and does not kink, so you are likely to avoid soggy spaghetti piles of sheets, spinnaker halyards, and throw lines if you use it. On the plus side, it is fast-running and buoyant. On the downside, Polypropylene is stretchy and has lower UV stability than Polyester ropes, so be prepared for a bit shorter useful life.
3/16 in is available in blue only; 7/16 in in orange and yellow only.