have started taking my young bitch to a therapy pool to do some swimming
Recently i have noticed that her undercoat   of    dark liver coat is showing through as a very much lighter shad of brown altogether This is not the breed standard colour i can see there
Do you think that the chlorine in the water could be the reason or is it her undercoat that needs to come out?

> Do you think that the chlorine in the water could be the reason

Could be. I know our local hyrdrotherapy pool advertise that they use bromine as being better for coats.

Possibly, she/he should be bathed in clean water post hydrotherapy!

I sold a red and white boxer to someone with a swimming pool. The dog was encouraged to use it often and never came to any harm but her coat turned to something like burnt grass...awful..but she lived a long and happy life.