It's a Bougainvillea, the star of the Mediterranean spring and summer. They grow wild in huge, effusive banks in the countryside in coastal/island regions of Spain, Greece, Italy, etc., and thrive in quite harshly arid conditions, so long as there is no heavy frost in winter.

The flowers are in fact the tiny white dots in the middle - the paper-thin coloured part (the plant is also known in English as 'paperflower') is technically a 'bract', a modified leaf.

Purple is a more common colour in the wild, and is particularly magnificent against the whitewashed walls common around the Med.