I'm too new to collecting irises to really have favorites, though I am somewhat partial to ones with blue-lavender and/or purple in them. (With DH, it is all purple, the darker the better.) I do have a fair number of whites, but that's partly because of the Moon Garden.
That said, though, I have grown to really like 'Afternoon Delight'... which is basically a golden tan. Maybe it's because of the lavender in it?