If it's an ensuite, it's nice to coordinate a bit and some people go a shade lighter or darker than what is used in bedroom. You can also go white on the walls for example and bring in the color of the bedroom by your towels and shower curtain for example.

I usually go half strength of the same color. We recently did my mother in law's bedroom in half strength Quiet Moments and her bath in full strength. Really pretty and seamless.