"Black is Beautiful" screams the hoardings in Ireland. Know what?

Question

when I was in Dublin and around a few years ago, all along the road, I found hoardings with this caption, "BLACK IS BEAUTIFUL". It took me three days to find out the answer. How abt. u?

Answer 1

Guinness  is good for you

Answer 2

Guinness is their national drink (Black)

Answer 3

Guinness of course what else could it be ?