When I am cooking small pieces of meat (so a meat thermometer is not an appropriate tool - I'm thinking of things like shredded chicken being stir-fried, frying or grilling slices of bacon, or minced beef being browned in a pan) I tell whether it is cooked yet by the change in colour in the meat. Chicken goes pink -> creamy white, bacon goes pink -> a different shade of pink, beef goes reddish pink -> brown, etc.

How does a blind, or colour-blind, chef manage? If going purely by time of cooking you will surely either end up with some pieces undercooked or the whole lot overcooked to compensate for that. Also it depends so much on the exact size of the pieces of meat, in the case of a grill how close the meat is to the heat, etc.

This is not a purely theoretical question - my husband is colour blind and really struggles with this. He cannot see the relevant colour differences at all, and although there are some texture changes on the outside of the meat, that doesn't tell you that the pieces are cooked all the way through.