To wonder why the add friend is grey and not blue (Facebook)

[outofcoffee]

Just that really, I've noticed sometimes on someone's profile it says add friend in blue and sometimes it's grey.
Does anyone know why?

I've never seen it grey, on mine it's a blue button.

They probably have friend requests turned off?

It could mean that person doesn't accept friend requests if it is grey.

They may have their profile set up so that only friend of friends can make a friend request.

I believe it also greys out if you have sent a request already but it hasn't been accepted as yet.

Maybe they blocked you?