Texels were brought to Britain as a white breed but, shock horror, you occasionally get a blue one. Maybe you could do some breeding to get purple from texels

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Occasionally grey shetlands can look blue too.
Then there are moorit Shetlands, Castlemilks and Manx Loghtans which are all a foxy red, in fact one of the Soay shades is reddish too. Usually the first cross is fairly boring, but further down the line the interesting colours come out.
It's worth finding out something about the genetics of colour if you are even having these thoughts PipKelpy. If sheep are too mundane, then try cats - you get about 5 per litter and the colours can be most amazing and unexpected, although I don't think there's a truly purple cat - plenty of blues to start with.
The person who did lots of research with both cats and shetland sheep is the late Stephan Adelsteinsson from Iceland