Thanks, Frank. I think the Claire De Lune flower would be larger. At least when it first opens, it should be yellow. There maybe light pink tinted flares at the base of the petals. THe bush is low growing like 24"-28". Your bush looks rather tall to be a Claire De Lune. In one of the post on Gardenweb, a poster noted that making the soil more alkaline may help bringing out more yellow in light yellow peonies. Maybe you can try that.
