Unidentified Gull Filey Brigg today

It's a sub-adult gull - the very last bit before true adulthood. When they are younger they have black bills and this is often one of the last things to change as it progresses to adult plumage/colour. You'll see it's beak not only lacks the red spot, but it is very pale and still has some black marks. Because it isn't fully adult, I wouldn't use leg colour to identify it either. It's one of the Black-backs but I won't hazard a guess which without some size reference. Someone might be able to tell you if it is Great or Lesser eg from beak size, but not me.