I guess Scotland is similar to Northumberland and Cumbria - but someone will correct me if I'm wrong.
It's dipping-time, and some breeds traditionally get some colouration in the dip. Animals being sold will normally be quite coloured, and any not looking orange (or grey or yellow or whatever colour normally used for that breed in that area) in the ring are likely to be penalised. For one thing, if they look white, they may not have been dipped - which means the buyer has to either dip or treat them again, or be especially vigilant in case they had not been dipped.
Because less farms actually use OP or equivalent dip these days, you can now buy 'dips' that basically just contain a dye... These will be used on sheep being sold so that they 'look right' in the sale and show ring.

Herdwicks are different again, I think. Someone from nearer the Lakes can correct this, because my knowledge is sketchy, but I think there is a red rudd that's rubbed into the fleece of Herdwicks. Whether the intention is to make older sheep look younger (they start nearly black and get greyer then whiter as they age) or what, I am not sure.