With a few exceptions, I can't think of many hardy ornamental grasses that I would consider colorful. Blue fescues have a nice bluish cast, and there are yellow and green varieties of it as well. Purple fountain grass is a deep red, but it is not winter hardy, even down South.

Many hardy grasses have colorful fall/winter color -- various shades of orange and tan -- but they are not necessarily colorful in summer. Pink muhly has probably the closest thing to showy flowers in a grass, but is otherwise a pretty nondescript green the rest of the summer. There are also many varieties of variegated grasses that have more of a silvery appearance from a distance.

To me, the main appeals of ornamental grasses are their form, movement in wind, fall/winter color, hardiness and resistance to deer and other pests. However, it might be very expensive to landscape an area as large as your spot sounds like -- unless you can grow the grasses from seed or buy plugs from a wholesale supplier.

If I were you, I would do a google search for ornamental grasses and look for a nursery that would sell grasses in quantity for lower prices. Blue fescue is very easy to grow from seed if you want to try it yourself. Northern Sea Oats is also easy from seed.

Recently planted 5 "Dallas Blues" Panicum, also known as switchgrass. If it becomes the color I have seen in pictures it will be striking! It supposedly gets 6-7 foot tall. In my zone 6, construction compacted clay I doupt it will get so tall. It has however hit the ground running and I look forward to seeing what it becomes! From what I have been told it does NOT self seed like a weed, like other switchgrasses do. I like the color I am seeing so far. One to look into. Good luck!

Japanese bloodgrass is an obvious choice for a low red colored grass.

I have to disagree with some of the opinions toward colorful grasses. Eragrostis spectabilis and trichodes have summer colors and busrt out in pink and metallic purple plume that put Muhlenbergia capillaris right next to one another. Miscanthus s. "Rotsilber" gives you great silver midrib and outstanding Red/Purple seed heads in late summer, and returning the green foliage to fire reds. Panicum v. "Dallas Blues" creates powder blue foliage and then blooms bright red/crimson flowers in summer, then transforming to a golden tan. Muhlenbergia japonica variegata would be a great variegated replacement to invasive Phalaris or Ribbon grasses, and exhibits a bamboo like appearance, as does Muhlenbergia dumosa, while green during the growing season, gives you shards of red, orange, and yellow in late summer. So, with the right combinations of ornamental grasses, you can have extended color throughout the year. ANd again, there are grasses that put on color from Spring throught Summer.

Hakonecloa can provide great yellow, Orange leaf sedge, Panicum Virg. 'Hanse Herms' reddens as the summer progresses, Japanese blood grass -- be thinking though about the likelihood that your blue grasses may be very drought tolerant, your yellows might need ample water and so forth. Most important is to plant grasses that make sense...just going on color can lead you in the wrong direction perhaps.