The original idea of mixing vegetables and flowers was based not in prettiness, but in pest control.
The following are commonly used for this purpose and the petals of the Nasturtiums and Calendula also make a colorful & tasty addition to salads!
Marigold (Tagetes)
Keeps soil free of nematodes; discourages many insects; plant throughout the veggie garden.
Nasturtium (Tropaeolum)
Deters aphids & pests of cucurbits; plant amongst tomatoes, radish, cabbage, cucumbers and under fruit trees.
Pot Marigold (Calendula)Plant in the vegetable garden to deter asparagus beetle, tomato worm and many other garden pests.