Capsicum - when to harvest?

My fruits are a brilliant green, yet the packet suggests I am heading toward a red fruit, and with a name like 'Redskin', the game is up!

The rear of the label says:

Redskin is a compact variety suitable for container growing. It produces high yields from early in the season. The 10 - 13 cm fruit mature from green through purple to red.

My lone plant is in a terracotta pot, that is well watered and fertilised every fortnight (alternating between Dynamic Lifter and Charlie carp). At this stage, the yield appears wonderful with the dozen or so fruit totally jostling for space in what is, essentially, a compact small bush. I guess this is why many capsicum appear a trifle pugilistic! The two largest fruit currently measure 7cms, so my guess is about another month on the vine. Must ensure they can feed 'grossly'.