Use bright flowers like petunias daises maybe colored grass
Maybe a garden statue
How about a bird bath with a circle of flowers?
I love the suggestions above. I would add some small bunches of flowers that are colorful. If you have full sun, you can try dwarf zinnias or petunias. If you have shade, you can try begonias and impatients.
A photo of your current situation to look at might give more direction to what might be suggested. The type and style of your house may dictate the recommendations as well as your location —->planting zone.
There are so many ways to improve the exterior landscape one of the most impactful ones I think— enhancing the curb appeal. Planters both hanging or upright…standing, windows boxes be perfect ways to bring color. Chose the colorful seasonal annuals or perennials best suited for your planting zone and sun shade exposure.
I personally find browsing the Houzz or Pinterest web sites to have some awesome visuals to consider —to collect all these image or storyboard for future reference, planning and execution. You might want to consider browsing over at these sites utilizing key word searches customized to your specific needs or interest.