If you're just charging it, the blue light should turn off when it's fully charged.
I'm not sure what happens if it's done charging charging it and you're using it at the same time. When I have it charging and it's turned on, the both the green and blue LEDs turn on and the resulting light is a light-blue colour.
nice thanks I appreciate it
I just charged the C5 while having it on. Once it's done charging, the blue LED turns off while the green one stays on.