Color of fried beef steak: sometimes dark, sometimes light-colored. Why? I have noticed that sometimes when I am frying beef steak it does not turn dark but it becomes rather light-colored. I have also noticed that those steaks that do turn dark during the frying tend to taste much better (more juicy, more like beef) than the light-colored ones.

Just today I was frying a rump steak which turned out light gray.

What explains those different results? Is it the beef quality, the preparation or something different?
It's quite likely that the steaks that ended up darker were dry when you started cooking them.

If you don't dry off the surface of your steak, the heat is used to evaporate the moisture on the surface, which ends up steaming the steak rather than developing a good char/crust.

The darker colors are the result of a chemical reaction that results in more flavorful compounds being created.

As for the juiciness, the higher heat (as there wasn't evaporative cooling) will brown the outside faster while leaving the inside more rare (and therefore moist/juicy).  When it steams, we leave it cooking longer, which can result in the middle overcooking (squeezing out moisture).