Cat I use a colour spectrum and plant opposing colours next to each other. Planting same colours next to each other usually results in cultivars just getting lost to the eye. Use whites and almost blacks for contrast to colours too. Only do mass same colour planting if your garden is more formal.
Height is also important: shorter ones in the front from where people are viewing; larger ones at the back. If you are viewing from above, like on a verandah or upper floors, this is not as important.
I try to view my garden from a distance to see what people are seeing. Daylilies are incredibly forgiving when being shifted if need be.
