The color changing process is calibrated as follows: When they turn dark purple from pink, that indicates that the band has been sun activated and sunscreen needs to be applied to the band. They turn from dark to light purple as your reminder to reapply, and from light purple to cream when you've hit maximum sun exposure for the day. They work with all sunscreen lotions, creams, and sprays SPF 15 or higher, and will even work in the ocean and the pool!
It's simple -- wear the band, reapply when needed, and avoid looking like the Red Hulk the next day.
For more information on Sunscreen Bands and how to purchase them, visit www.sunscreenbands.com.