Last year, when the algae got thick in the pond, the bass had a washed out appearance, almost as though they had been bleached.

The lateral line was barely visible, and even the back was lighter than one would expect.

They stayed that way until the cool weather set in and the algae began to die off.

This year, the algae started earlier than last, and the contrast of colors began to fade.  Then the rains came.  Whether due to the rain, or some other reason, the algae diminished considerably, with algae only in the top inch or two, and only "thick" at the windward side where the wind had blown it.  

As soon as the algae thinned to just the surface, the bass, immediately darkened up.

I know some species of fish, maybe most for all I know, have the ability to "adjust" their coloration to their surroundings.

I did not realize they could do it with such rapidity.

Thats a very neat observatioin Rhino, I new they adjusted depending on water clarity but had no idea it could be done that fast.  

A bass's coloration depends on sun penetration. the more contact with the sun a bass has, the darker it will be. If you notice when you catch a bass in deeper water, it will be a lighter color. Shallow water bass are a ton darker. The bass in you pond didn't have the sun on their back because of the algae, so it didn't matter how deep the were.