Beauty is certainly in the eye of the beholder but from an historical perspective it's was about the correct (and I use that term advisedly) of colour and shade to balance the sett. It is very, very rare to find an old, by which I mean C18th specimen, where all the colours are of a uniform shade as so commonly occures with commercial cloth today and which in my eye kills too many patterns. The other thing to bear in mind is that colour and shade are not the same thing and people often use the former to mean the latter.