Why has it faded?

I bought a bright red fluffy tree plant - otherwise known as Astilbe Fanal.
It was so nice the bright red, it had to be red over the pink and white.

However, popped it into a slightly bigger pot and the bright lovely red has now gone a very dull wine red.
Why is this? It's been fed.. watered.. :(

 

Is it just that the flowers are finishing for the year?

 

I would be surprised. It was almost overnight change very quickly after purchasing.

 

Oh that's good! I am glad to hear it.
Is it a good one to survive against snails and slugs?
I havent noticed any nibblings but it is in a raised pot, but i am thinking of putting a few in my borders.