With no cells in , the LEDs are green ... When charge is ended also LEDs are green ... When charging , the LEDs are red.
The left hand side open circuit voltage is 4.25V and the right hand is 4.24V.
When the green LEDs come on , both cells are 4.22 volts (open circuit) and after a one hour rest , they settle to 4.21 volts.
The only slight problem with the charger is the length of time it takes to get from 4.1V to 4.2V ... Seems to take ages.
It is still a worthwhile charger though ... I use either this or my Soshine SC-S2 ... I had to use both chargers the other day as I was topping up four part-used 18650s ... The Soshine is faster but it really isn't that important as they both end up with the same final voltages.
The main thing to remember is to take the cells off charge as soon as you realise that the LEDs change colour ... I check every half hour or so to see the LED colour and I also check the cell temperatures ... I also remove the cells occasionally to check the open circuit voltages , though I must admit that I am doing this less often than I originally did.
I check the cell voltages when on charge and when I see that the voltages are near to 4.22V , I know that they are nearly ready to come off the charger.