What kind of bug is this? I found it on my Cleome plant in Atlanta Georgia
This is an instar (nymph) of a shield or stink  bug (order Hemiptera, family [Pentatomidae])(https://en.wikipedia.org/wiki/Pentatomidae).

Specifically, it appears quite similar to a later juvenile stage (~4th instar) of Chinavia hilaris, the Green Stink Bug. 



 4th instar; Source: Oregon Dept of Agriculture 



 4th instar; Source: UF IFAS; Credit: Herb Pilcher, USDA-ARS, Bugwood.org. 

Alain Hogue also captured a wonderful picture of this species at bugguide.net

From UF IFAS:


  Distribution 
  The green stink bug occurs in most of eastern North America, from Quebec and New England west through southern Canada and the northern U.S. to the Pacific Coast, and southwest from Florida though California. This is the most commonly encountered stink bug species in North America.