Meaning of "for all their colour"

What does "for all their colour" mean in the following sentence?

Standing immobile throughout the day, these vivid objects, with their fantastic shadows on the wall behind them shifting and elongating hour by hour with the sun's rotation, exuded a kind of darkness for all their colour.

Excerpt from Gromenghast by Mervyn Peake.

I have not been able to find the meaning of this expression in online resources.

It's a specific form of "for all (pronoun) (quality)", e.g. "for all your years of experience, you can always learn new things".

It means that despite having the named quality, surprisingly, the object has another quality that would seem to be contradictory.