Colored urethane belting is normally made by adding colorant to cord while it is being extruded. In this process, called "extruded color", the colorant displaces some of the urethane. Since it dilutes the urethane, it is technically a contaminate that reduces the belt strength. Small amounts of translucent colorant have minimal effect, but large amounts of opaque colorant can reduce belt life measurably. Therefore, the greater the quantity of colorant - the shorter the belt life.
In 1993 we developed a proprietary process that lets us color belts AFTER we make them. We call it "Retro-color". The colorant does not displace the urethane, but rather fits in between the urethane molecules. Retro-color will not rub off because it actually penetrates the belting. Nevertheless, the amount of urethane in the belt remains the same, so the life span of the belt is not changed.
Some colors work better than others. All are translucent except black. Red and blue look vibrant and shine like jewelry. Green, black, violet and gold look fine, but yellow and orange are not recommended because they come out straw colored.
Retro-color does not reduce the strength of the belt. In fact, it seems to increase it. We have not verified this; however some college girls wore our 1/8" blue and red O-ring belts as bracelets to a party at Ohio State University. They challenged Buckeye football players to break them. It took two tackles using their hands and their feet to pull them apart.
It is possible to color belts with more than one color, e.g., we made one that is red, white and blue. Such multi-colored belts have a practical application - you can see from afar that the belts are in motion.
For small quantities retro-color is often less expensive than extruded color, because extruding a colored profile usually entails a large minimum quantity, e.g. 5,000 to 50,000 feet, and delivery can take weeks. On the other hand, we can retro-color a single 3" long belt in a few minutes. The only drawbacks are that for large quantities, retro-color is more expensive than extruded color. It is also not food grade.