Annodized steel rings are great! Extremely light too. In the annodizing process the steel is melted away by the acids leaving only the color. Really stands out in the sun, your pilots won't have any trouble picking up the wrong lines.
Or you could use a short colored piece of leader line to the rings, Mason line can be found in florescent pink, yellow, orange and green at contractor supply houses that sell to the masonary crowd. You'll have to check on the line strength to get a piece strong enough, but its out there. I had been using it for years on my winch and bungees. Since its a short piece you don't have to have that strong of a piece, and of course you can double it up. Gordy ************** Biggest Grammy Award surprises of all time on AOL Music. (http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp00300000002548)
