One of my favourite things in photographs are colours that are aesthetically pleasing.
With animals, I'll either try to compliment the background to the fur or eye colours. The emerald green was a fantastic compliment to the cat's eyes.
If the colour is off or too dominant I find it takes the attention away from the main subject. Colour should be there to enhance the details of the subject rather than distract.
Great image! Did you actually shoot on this background or is it added in post?