It fascinates me how many wildflowers vary from their standard colours, often changing from pink to white and vice versa. Here we have Centaury, usually pink but also commonly seen with white flowers; Knapweed, also usually a pinkish lilac, but I occasionally see a white variant; Thistles that are also usually pinky lilac but often flowering white hereabouts; and the usually white Yarrow, which I find growing with quite pink flowers in a local field.