Yes can be used in a reel the flexibility is great
This, as in any product, should only be used for it's intended purpose. This hose is designed for air not propane. I wouldn't recommend it for that purpose.
I haven't ever seen that in my use of these, including dragging it around on white floor moulding. I can imagine that from the factory some red dust can be on the hoses, since they cut hoses and press the ends on. Maybe that it the only place it comes off on hands and shirt. Obviously if its abraded on concrete or edges the rubber can degrade, scuff, and some particulates can come off, just like black 'dust' from a burn out of a tire on a hot rod. But generally rubber and its color is very stable. As for treatments, I not suggest anything on rubber, for any reason, except maybe if you had it outdoors exposed full time, i'd guess the sun will bleach it out and ruin it like tires on a trailer or old car parked in the weeds. Then some kind of UV treatment, like ARmour All, designed to preserve - as long as it doesn't degrade rubber, like some solvents and petroleum will do. If it was me, i'd cover it in a pipe or conduit for long life. good luck.