Best, Anne H.
Answer: It appears you live in the UK, so I am going to assume your weather is a little more temperate than on this side of the pond.
You do not mention if you are looking for full sun (at least six hours) or shade, so please check the sun requirements for the suggested plants.
One of my favorite plants is Bougainvillea, which is available in several vibrant colors. It is considered a tropical, so it would need cold weather protection. There are several other options in our Flowering Plants category. Check out our Annuals: Calibrachoa, Osteospermum, Lophospermum, Bacopa, and Lobelia. In the Perennial section there are lots of options like: Agastache, Baptisia, Centaurea, Delphinium, Digitalis, Eupatorium, Echinacea, Liatris, Lupine, Nepeta, Penstemon, Perovskia, Phlox, Salvia, Geranium, and Veronica all have varieties in your color options.