Zinnias are easy to grow and come in all heights, colors and flower types.
A nice combination is the lime green and pink. Then there's the Profusion variety that live up to their name with blooms everywhere. This plant is shorter, has a full shape and blooms can be found in yellows, red, white, orange, single or double, plus is not prone to powdery mildew
Gladiolas bulbs would create a showy space.
Geraniums love Sun, too, as do petunias. For height add some Victoia Salvia (an annual).
I'm thinking all annuals here for continual color, and ease to grow. Zinnias can even be started by seed in the garden.Happy planting