Acara changed colour?

[Diamond]

The other day i was cleaning the aquarium out, changed the water, and cleaned the rocks etc, there was nothing in the tank at all, i went and sorted the fresh water out, and when i came back one of my blue acaras had completely changed colour, before she was vertually black, but she had changed to a completely washed out dull pail colour, the colour of the gravel vertually, do they change colour to there surroundings, or could she of been a bit stressed, she soon changed back to her normal dark colour in 10 minutes.

[benneb]

She was probably just a little stressed from the water change. I have some young firemouths in my tank which get stripes across there body when I do a water change, making them look like Convicts.