Centranthus ruber (Red Valerian)
Introduced from the Mediterranean, but common in the UK, especially in the SW, on cliffs, old walls and rough stony ground. Part of the interest lies in the neighbourly coexistence of three common colourways:
1. A deep pink, a very common colour in insect-attracting flowers, more or less the same as red campion. (Whether you call this magenta is pretty much a matter of taste. For me the plant that defines "botanical magenta" is common vetch. In other words I think of magenta as an intense red-purple, rather than pink.) About 50% of the population are this colour, I'd say, based on many miles of Mendip streets.
2. Crimson, looking somewhat reddish in comparison to the previous. This is nearly as common as the previous, maybe about 40% of the total.
3. And white. Perhaps a comparatively sparse 10%, but still completely commonplace. (I don't understand the genetics behind this.)
Very much less frequently, (like, .00001%) you might come across this pale pink form.
The vivid colours make Centranthus ruber welcome in all but the most snobbish of town gardens, until it gets too invasive. But the classic location is on the outside of garden walls. Throughout the summer the plants narrow the streets on both sides, leaning inwards like arsenals of soft weaponry drawn up for a massacre of love. Then masses of fluffy seeds get blown into stony crevices and develop into even more of these tough, vigorous plants.