I suspet that you may have a "celstar" patternned iris here
From: thomas silvers <email@example.com>
Sent: Wed, Apr 14, 2010 1:40 pm
Subject: [iris-photos] HYB: "Clean Amoena"
This seedling (garden name "Clean Amoena") has buds that are fairly noticeably tinted with blue/purple. These open to nearly pure white flowers, but sometimes can show a faint amoena pattern.
It's from (Kupari x Rosemary's Dream) X (Kupari x suaveolens var. rubromarginata).