Here is a key to get you started identifying examples of wild Pacifica iris. To move through each step, you follow the single most correct of the two options given. If a feature is not visible, you can supplement this key with additional information from the species' descriptions, or from more extensive keys like the one Lee Lenz first put together in his 1989 report: A Revision of the Pacific Coast Iris, or Carol Wilson's recent review of the genus Iris in The Jepson Manual: Vascular Plants of California (2011, pages 1357-8).
The key cannot be relied upon to identify hybrid plants - the result of a cross from different parent species made by a plant breeder in a nursery, or by bees in a garden or in the wild.