No, I have just been pulling them out before they contaminate the native yellow ones.

Actually red cowslips are natural. They are just a form, or aberation, of the yellow cowslip. I am quite sure that they are also available as cultivated plants in garden centers although I have never seen them.
Did you know that they are red because they have been fertilised with bulls blood? Or that if you plant a cowslip upside down on Good Friday it will come up as a primrose!

Chestnuts!
If you plant a cowslip upside down on any day of the year it dies.
Red Primula veris come from contamination with pollen from a red flowered variant of Primula vulgaris from the Balkans. The only red native Primula is P. scotica which is found only in Scotland and Orkney and flowers so much later that crossing with the others is difficult. Primula farinosa is pink and found only in Yorkshire and Cumbria.

now now its not april fools day just yet.

I noticed a lot of cowslips returning to the sides of motorways and other places, also on National Trust land. Much shorter than the mental picture we have of them, but very lovely.
I don't think I feel like planting anything upside down on Good Friday - my life's quite complicated enough already thanks! I'm content if my socks match and I remember to brush my hair now again. As for tinkering about with cowslips - well!

I have a red cowslip in my garden in it is amongst the yellow ones.......