Sea shell is orange, almost in the middle of the pure red of snow and the muted yellow-orange of Old Lace.
Old Lace is the "dirtiest" of these whites, with most color and also the color there is in this is a bit dull, and not pure.
Don't you think that "Old Lace" and "Snow" are "summer" palettes, and not for "spring"? Old lace is actually very warm and more "autumn" than "summer", and the periwinkle in "Snow" palette is a "spring" color...
I might be an "autumn" anyway... but I kind of don't care ;-)