
I like to mix yellow
hems with those of other colors that have yellow throats.
Some of the throats are so dominant that it looks like you have wonderful coordination
without even trying. And yellow livens everything up.

Shasta Daisies, with their yellow
centers also coordinate effortlessly with almost everything
except maybe near whites.
Hydrangea foliage contrasts nicely with daylily leaves so long ago I bought EMPEROR BUTTERFLY because
it seemed like a good
compliment to Hydrangea 'Pia'. Of course, EB, when it is blooming,
far outshines its companion. 
Back to combining daylily
with daylily: Another opportunity for coordinating is matching
an eyezone color to a companion. It helps if the background of
the eyed
cultivar
matches the companion's throat. This combo happens to be ETCHED
EYES and LOCH NESS MONSTER, and also planted nearby is LAKE NORMAN
SPIDER, which doesn't show in this photo.
Below Loch Ness Monster and Wiregrass Greenstar.

Edges
can also coordinate with surrounding plants like BEAUTIFUL EDGINGS
with a rose pink. I have it next to WOODSIDE ROMANCE, which is
considerably shorter, (really) but the colors still look nice,
I think.
The best combining I've ever done occurred when the daylilies were blooming in their pots and easy to move around,
but that isn't usually an attainable luxury. If you have too many clashing colors, white is a great mediator.
Daisies, or Cosmos 'Sonata White', or fever few, or even white impatiens can help separate warring color tribes.
Blue is also excellent with most daylily colors, but harder to produce in the garden,
Roses and daylilies mix well, especially the carefree kind like "knock-out" or "carpet roses".
Pansies are very attractive with early bloomers, though, of course, they don't go very far into really sultry weather.

Remember, though, nature manages pretty well without a color wheel, so if your garden shows all the colors of the rainbow and then some, rejoice in it.

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