A few more Dahlias
I think Dahlias come closest to water lilies in subtle color changes within a single flower. We've had such good luck with them this year, I'll definitely look through the online catalogs to find named varieties. The only problem is finding places to plant them as they do take up a bit of space which we are quickly running out of. Here's a great site with lots of photos, that 'Peaches and Dreams' is an eyeful and more here and here but you have to search by color.