While Im not colorblind and I have alot of experience cooking. Hubby accidentally brought home a work thermometer once and I thought dinner was done. Decided to use it and I was 30 degrees off.

For safe food there is NO replacement for a thermometer. These days I still try to know when food is done and I still check my senses with a thermometer. Still after all these years im off about 50% of the time lol Though my temperature margin is better 10 degrees as opposed to 30-50.

I dont use a thermometer for grilling steak or pan cooking usually. But if anything is done in the oven or thicker than a steak i use it like for grilling chicken.