If the beds get a lot of sun, marigolds, zinnias, petunias will all do well and give you a lot of color.
First, where are you located? This will help us figure out your zone.
Second, what kind of exposure does this bed get? Full sun, part sun, shade?
Third, how big is the area?
Fourth, do you want annuals, perennials, a mixture of both? Just instant color?
If you could edit your question, we can help you further.