Day 19 just a few hours bevore day 20 startet. One ore two eggs always pip on day 19 most of the others on day 20.
As mentioned above. I always have one ore two eggs that pip early. Would not be concerned about that.
Hatch:
My chicks stay in the incubator for 48 hours to let them dry...
Only Info I found:
Of course, mix chicks can have any color variation at will (genetic inheritance). Which in turn means that the identification color of mixed chicks does not have to be correct.
I just keep them in my basement with the other eggs. I store all my eggs with the pointy side down (keeps them longer fresh). No turning (Saw a Video of someone who tried all different storing methodes and there was no differenc in Hatch-Rates)