Blue light on Airpods Pro

I noticed a problem with my Airpods pro so I tried to restart them. My surprise came out when I saw a blue light coming from inside the box, I supossed I came from the Airpods Pro itself. It happens when I try to restart them. When the orange light flashes 3 times, them from inside the box comes also that blue light that flashes also 3 times. And it stops if I take one Airpod pro out of it.