Why are large mouth bass in my pond grey?

Sometimes hard bottom bass with little vegetation in the water, and lots of rock will be lighter in color.  I have fished some rock pits that produce lighter color bass.  They blend in better to their surroundings and don't stick out so much.  

In our south florida lakes with all the veggies, they are usually dark in color, and blend in with their surroundings.  it's all about ambushing bait.