Why do my big toes pop/click when I walk? It doesn't hurt. It's not discolored. It's done this for years.

If not painful. Don't worry, could be from bone spurs, arthritis tendons etc. When painful then see a doctor.
Pop lock and drop it. I would not be concerned about the popping. Some would say early arthritis is setting in, but sometimes the joint does not properly align and slip in and out into place occurs and you can hear a popping out clicking. If pain starts to occur try setting a podiatrist.
Benign. Any joint can make a popping sound. There is no harm in it. The sound of popping vertebrae led an ignorant man last century to think he was "adjusting subluxated vertebrae" by means of which he could cure every known disease. This is the theory of osteopathy which morphed into chiropractic. Science has moved on since then.