If you have a nondescript concrete patio, paint is a great way to add character and interest without spending much money. Keep in mind that the paint will wear and age much quicker out in the elements than it would inside, but that is part of the charm. If you want to DIY this, read here.
I'd stay within colors you find in great quantities in nature, blues, greens, terra cotta. Saturated colors will work best since they will fade. Use a color that is complementary to your house & trim paint.
While more laborious, a painted pattern will add character, check these out from Finnish blogger Liivian Talossa on Apartment Therapy.