Very interesting indeed Marigold, particularly as we have some. Have experience of hybrid coloured egg layers and have indeed been able to wash the colour off. We noticed the 'ear lobes' on ours were sky blue, the same colour as the eggs.
Nice to see that he has a proper fondness for Orpingtons too, Chris!
I can't wash the colour off the eggs from my Cream Legbar, Nutmeg. She has just started lay again after her moult and break for the winter and her eggs are a much darker blue than they were by the end of her lay after last summer.i suppose they use up their store of pigment gradually over the weeks of their lay, is that right?