Actually as of today, there are 69,257 daylily cultivars registered, so we can say that there are close to 70,000 registered daylilies!
I grow not only daylilies but other companion plants. Just had garden tours here today and although people were asking about the daylilies, there were a lot of comments about the Perovskia ( Russian sage) people said they'd never seen it grow that big; the Purple Monarda 'Prairie Sunset' ( unusual color of monarda) and the most comments were about the Orientpet and OT ( Orientaltrumpet) lilies that are also extremely fragrant.
Another perennial that got a lot of comments was the chartreuse foliaged Agastache,'Golden Jubilee.' I love the chartreuse foliage.
Here are a couple of garden shots from the past couple of weeks. You can see some of the perennials I mentioned.
Liatris in foreground, Agastache'Black Adder' and Nepeta 'Walkers Low' also in this picture.

As to your first question, I would find a bed of all one color monotonous. Only you can decide. Daylilies do need to be divided every few years so it depends on how much work you want to do. Daylilies grow at different rates so some clump up faster than others. The more you plant, the faster the bed will fill in. When it comes to fragrance, I can't smell any of mine, you would have to ask my dog. She prefers Betty Warren Woods tho. Here are some of mine:
I thik this one is Siloam Virginia Henson

This is Swiss Mint, a mid to late bloomer.
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This is Strutters Ball, purple, and Prize Picotee Multiflora, both mid to late bloomers
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This is my favorite, for now. Dominic.
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Rosie's favorite Betty Warren Woods
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Aramis, one of the first ones I bought. I have it planted with a white phlox and an ornamental grass
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So far I have mostly mid to late flowering daylilies. I'm working on getting earlier ones. Hope this helps somewhat. Marg

Julia thanks for the information on your camera. Your garden photos are breathtakingly beautiful...Betty

Do you know the name of the tall white Orienpet lily in picture #3? What was the information on the camera? Did I miss it?

Daylilies come in so many varieties, that it seems a shame to plant one color only! You have to decide a general idea on sizing-they can be about 12" high to 40 some inches high. Or would you want a bed that would be graduated in height-short in the fromt and ending in something like asian/oriental lilies. I have some 'tree lilies' that grow about 5'. Some daylilies are fragrant, but most don't have a strong fragrance. The lilies are great for that.
Other companion plants are coneflowers-many pretty colors now. Liatris (the purple feathery thing in floota's picture). Daisies and Rudabeckia (black eyed susan family, poker plant, coreopsis, and Sedum makes good fall color.
A few older, hardy daylilies that have done well here:
Condilla

Gorgeous flower beds! They're so beautiful, they almost don't look real! It seems I need to work on the drainage and sunlight for my lilies (and other plants), esp. since our 80 y.o. Norway maple now shades it for much of the day.

The Oriental Trumpet ( Orienpet) lily you are asking about is Conca D'or. It really is great- extremely fragrant and huge blooms. It increases really quickly and I will need to lift a few of those bulbs out this fall.Yesterday ( club tours of the garden) a lot of people were asking about that lily as well as a double pink oriental which I can't remember the name of! Lilies make good companions with daylilies but you have to watch them because the bulbs increase so quickly. Where I planted just 1 bulb 2 years ago, there are now 4-5 large stalks and a lot of little ones.

I believe the Camera question was asked on another thread, but I use the Canon EOS Digital Rebel. It has come down in price $400 from when I got it years ago. That's the good thing about electronics!

Aloha, Daylilies in my Cottage garden has been a learning process for the last 3 years. You can't do better then to learn from the folks on this forum. You can go back through the many posts to see the many fabulous faces of Daylilies. The more you look the more you will define and refine your taste. The other considerations is the bloom times. You want a selection of early, mid-season and late bloomers to extend the show.

If budget is a consideration as it is for me, don't loose heart. There are so many in the $5 to $20 range, usually older varieties that can fit any color theme or loved form. There is no reason to have anyone less then ones you've fallen in love with.

Floota's garden as shown in her generous photos above is a stunning blue print for what is possible.I am so excited for you, as you start this adventure of discovery. Along with this forum, a tool that is invaluable is Tinker's Garden Daylily Database. Bookmark it. You can do a search on any named Daylily for it's stats and photos as seen in gardens. You will notice that the color and form of a particular daylily may vary between the 3 photos shown. This is due to different growing conditions and the time of day the photo was taken. I cross reference the photos seen on nursery sites with Tinkers to see what is consistent, and then take it with a grain of salt. lol. The photos and descriptions posted by this forums members from those with MY same zone are what I trust the most. If you can do a day journey to a daylily farm/nursery, do. Nothing like seeing them in-person.

Make sure you use the search feature on this forum to see old posts on particular areas of your interest. For example- " favorite Corals" "True Pinks" "Late bloomers"
Companion plants etc.etc....Good luck, enjoy!

Killer Bed phots! I really like the colors on Merry Witch. I had missed this, so I'm glad I went to page two and found it.
kay