^ This is one thing i'm not actually sure about... since once mine changed to that brownish color, i didn't bother trying to force him to change back to a red color...
Although i guess in theory, it should work something like that, since from what i've observed, they do seem to try and match their surrounding colors as much as possible... mine even use to have little tiny flecks of green spots if you looked closely enough, i think to try and mimic a bit of the plants in the tank...
But normally, form what i hear, people who do have red congos, tend to keep some type of red substrate in their tanks to help keep their congos coloring...
