Solid Colour Bikinis
No print, nothing to clash with. A single flat colour is the easiest swimwear to wear, the easiest to put under a patterned cover-up, and the thing most people come back to after a season of prints.
Black is the workhorse, white and cream look their best against a tan, and the brighter reds, greens and blues photograph well without needing any pattern at all. Cuts run from simple triangle tops to structured one-pieces.