PlantFiles: Japanese Morning Glory
Ipomoea nil 'Gray Lady'

That's a great note from Ron_Con.
I also grew mine for the first time this year. I started it indoors in Apr. and earthed it late June. It grew well and hearty. It began to bloom the first of Aug. The first bloom was mauve! That went on for a week or 2 and then the whitish gray game along and blooms about 12 or 14 blooms daily. At least twice a week, the little mauve one appears. It's almost funny. Will post pictures soon. A sweet vine whose lovely 4" blooms were worth the wait. Will surely plant this again next year!

The term "Gray Lady" was first used to describe an Ipomoea nil cultivar that was selected out over 20 years ago by a veteran morning glory growing lady in Kansas and was offered for open trade in the earliest editions of the printed trade publication known as the "Flower and Herb Exchange"
I have added for reference this important footnote to accurately document the history relative to this cultivar, as there have been some 'incorrect' claims to a more recent origin for the cultivar 'Gray Lady"

The vine is a vigorous grower, but the flowers don't last long into the morning like most I. nil cultivars. The buds start out as a pale, delicate pink, then bloom nearly white with the pink cast barely discernible, fading to a darker, more obvious pink as the blossom dies. I really like it, but I'm disappointed the flowers don't last longer than they do.

Very pretty pastel grey with a hint of mauve undertone. From certain angles it appears to be a shimmery white but will change as you move angles...This is a very intresting flower of about 4 inches in diam. but this is also the first year for me to grow it and these are my first flowers so I may ammend my comments later.
Dee