I'm looking for a small shrub that stays about 30" by 30" and likes full sun. Red would be my flowering preference with yellow in second. Please no spirea.
Potentilla is a workhorse shrub. Best used in groupings, but tough to beat for tolerance and dependability. Hypericum kalmianum (Kalm St. Johns wort) might be another one to consider.
How about a rose? 'Knock Out' rose was developed in Wisconsin and is around 3x3, maybe 4x4 but can be kept smaller.