yellow or blue?

The great egret (Ardea alba), also known as the common egret, large egret, or (in the Old World) great white egret, or great white heron. Like all egrets, it is a member of the heron family, Ardeidae.

It is interesting to note that in breeding season they grow out these long feathers that they fluff up, and their yellow beak becomes black and their faces can turn quite blue.

And here seen again with this couple...who are mid courtship with the wonderful bill clappering that they do, where they touch beaks.