Blue would be nice, not a very dark blue like black &blue but rather like Salvia farinacea, the light blue version (or the white one). Hardy Geranium Rozanne, Orion also would look great in front of the plant. I have Plumbago (Capewort-??spelling) around FC and it looks great but Plumbago would not be hardy in your zone.
White is the other color that would look great. You have to decide if you want some groundcover type like Alyssum (although alyssum usually melts away in the very hot months) or you want taller companion plants like white Oriental lilies, white Foxglove, or Delphinium or bellflowers - all these 'spiky' plants in blue would be great, too. You can throw in a few Nigella seeds in blue and/or white, but no pink! not only their flower color is very nice but their ferny foliage looks wonderful around roses. Nigella is an annual but if you let the seedpods on (they are attractive), they will self-seed.

I love my Fragrant Cloud. I have plumbago(creeping) planted under it and it has returned for several years and I am in zone 6. Love the blue with F.C. I am looking for a rose to plant beside F.C. with no ideas. Considering Plum Frost. Any ideas welcome. My vote is for something blue around your F.C. Lesley

I have my FC next to Mr Lincoln, and in my yard, the colors are too similar. So I'm considering moving it. I have a patch of crazy daisys that are white. I though FC would look good in the middle of them.

Blue is a nice thought too.

Geranium 'Rozanne'. Wonderful, wonderful plant.

Screaming yellow or orange daylilys (not the Hemerocallis known as "ditch lilys", though--they spread too quickly--pick slow spreaders and they'll be fine for years).

I'm with Hoovb: Geranium Rozanne goes with pretty much any colour rose, just a gorgeous mound of blue and it blooms non-stop all summer. You can't beat it.
Judith

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Blue is great. I have Love in a Mist. I love the Geranium picture and idea--even the foilage. I have a "Johnson's Blue" geranium but I had to move it from full sun to bright shade. It blooms prolifically in May and then slowly quits to about mid June then, that's it. I will research the "Rosanne" to see if it is different from the J. B. I have another quiestion. When you plant a companion plant with the roses, where would you plant the geranium or even the Love in a Mist?? I want the rose to get enough air circulation and would want to be able to mulch and weed. So how far away do you plant a companion plant?? I like the idea of Rosanne, as for me, geraniums don't spread very rapidly and would not get into the rose bush. I have a few roses but have not had good luck planting companions with them--they start crowding the plant. Thanks for the suggestions, my computer has been "sick" so I am a little slow at responding. I need to complete the research for all the flowers you suggested.

Eden, Rozanne blooms far more than any other geranium I have grown so far, especially Johnson's blue, and does fine in full sun. It also spreads out quite a bit, just the long mounding stems, not the actual plant. So far (three years) it hasn't invaded the roses' space. I plant it about 1-1/2 to 2 feet from the roses, but by summer there is no bare ground showing. It's low enough not to interfere with the air circulation, and once I mulch in late spring, and the geranium covers everything, I don't find I need to weed. (maybe there ARE weeds under there, but if I can't see them...oh well..)If it gets too close to the roses, just whack it back. It won't mind a bit! Catmint Walkers Low is great too, but will spread more. So far, I've just dug up the new baby plants and moved them elsewhere, it hasn't been any trouble to control. Have fun choosing!
Judith

Since I have a lot of apricot and yellow and other warm colors including Fragrant Cloud, I plant Salvia Coral Nymph in between and also use a very similar geranium to HoovB's, altho I can't remember its exact name. I just tore out some white bacopa (now called sutera). It likes a bit more shade than my rose garden can provide. But its pure white flowers are nice with roses.
I like the idea of fireworks surrounding the rose bushes. The salvias need very little water and I shear them back when they start crowding the roses. They attract lots of finches and hummingbirds. Gaura is another plant similar to the salvia in the fountain-type way it grows. Other whites that work well are pentas and shasta daisies. Foxgloves, calla lilies, nemesias, over time I've tried and enjoyed them all. Thyme also looks good under the roses and it comes in whites, pinks and blues. Hope this gives you something to consider.
Mary

Thanks guys, I will do my research on these flowers.
See where I can buy them. And get busy!! I appreciate the information.