content: As you probably know, the balls are only for shade so the sunlight doesn't cause too much bromate in the water + there are other benefits like deterring birds.      Basically they tried testing different colors but the dye was unstable and the company producing them couldn't guarantee they'd last more than a year in the sunlight. The black shadeballs are coated in a thing called carbon black and are naturally black without the use of dye. As they are with the carbon black and no added dye, they'll last 10+ years.