This seems to have evolved in us in response to one of the evolved functions of flowers which is to provide information about the plant. Our appreciation of the beauty of flowers may well be innate or instinctive and be an adaptive response to colourful cues in the environment which originally helped primitive hominid species to find sources of food. With experience flowers tell us a lot about the ripeness of a plant's fruit. Plants use flowers, the reproductive part of the plant, to attract animals and insects to assist in their reproduction through pollination and the spread of seeds. Contrasting colours within a flower also help make it more visible to insects and animals.
Flowers are often most colourful when they are mature and ready for pollination.
Colourful bilateral symmetry in a flower indicates that it is more advanced. Pollen analysis revealed that the body of a man had been placed on a bed of flowers. Why is not known but one suggestion is that the perfume given off by the flowers helped to cover the odor of the decomposing corpse. Genes seek to reproduce themselves through having offspring. This, of course, is not conscious but just the way it is.