I didnt think this was a unique thing, though obviously not as common as your standard brock else we would see lots of yellow-uns at the sides of roads, it was just that it had all its perfect markings only they were bright yellow rather than grey. The rest of the brock was white as the driven snow, which gave such contrast to the yellow. Im sure though that there are many variations within the different albino brock, so what i saw as an albino/yellow brock, might be quite different from the next moochers sighting of one.