I tried to get a better picture of this particular Iris purpureobractea seedling that shows red/purple foliage margins coming down through multiple generations from Iris suaveolens var. rubromarginata (it's great grandparent).
The second picture (also showing a terrible need for Spring cleaning) shows the foliage of the pollen parent that carries the red-margin trait but has it obscured by PBF (purple based foliage). This plant, garden-named "PBF-RM", is from a cross of: the best margined seedling from (KUPARI x suaveolens var. rubromarginata) crossed with the best PBF seedling from (KUPARI x ROSEMARY'S DREAM). This seedling had the second best combination of PBF with red margins. Its sibling with better foliage pigmentation had horrible flowers.