One specific light illuminates for each device that is actively charging. Anywaaay, I wore them to work today. In the summer they would be great for outside or at the pool. The color has held up well and it isnt fading or rubbing off anywhere. I used the app (later more about the app) to create my own personal frequency profile based on my hearing, but with that enabled the highs were to stong for me, so I ended up with turning this off. These sandals fit perfect,almost feel as if I have no shoes on. Full of hope that I still made the right investment, I contacted the customer service. Very lightweight but I imagine for a young active boy these wouldnt last a month. With 18 different colors, I can mix and match with my outfits and bathing suits. I then decided to try and update the firmware.