Everyone has different ways of organizing irises in a bed, whether by height, bloom season, hybridizer, color, or a combination of those things. For me color is the biggest thing I look for when deciding which cultivars to put together. Lately I've been getting more fancy with picking solid colors to pop color out of multi-colored varieties.
Here is a picture of Breakers and Picasso Moon together that I think really sets off each other's colors. They're close to being opposites on the color wheel.
In one bed I put clusters of cooler colors on the left and warmer colors on the right.
And sometimes it's just random prettiness (Daughter of Stars and NOID light peach).
What colors do you think look nice together? Do you mix and match different colors, or have a bunch of monochromatic tones that you like together?