VERY roughly (I'm sure a proper Welsh speaker will send in a thousand corrections):

Are there any more goats to milk?
There's an old one mooching around on the craggs and rocks.
Its a white, white, white one
With a white mouth, white mouth, white mouth
And a white tail, white tail
A white arse and back
White white white.

Then ddu is black, goch is red and las is blue.