I've been watching this lemon seedling carefully this year (it is now in a #2 pot, sitting in a non-draining flower box), and the opening has been variable. I've had good opening (as seen in the image above) after cool nights, and I've had poorer opening (and paler color) after cool nights. I'm not sure if it is a succession of cold nights or crossing some marginal temperature threshold that affects the opening and color, or if I'm not keeping the pot watered enough. It is certainly an EMO, but some days it just has better looking flowers, color and opening wise, than on others. After yesterday's cool and rainy day (63 F per Accuweather), and a low temp last night of 52 F for our city (maybe cooler at my house, we are in a bit of a depression), today's blooms opened pale and flat, and with the cool temp (high of 67 F) and all the overcast today, they pretty much stayed that way.
(Pretty much everything today was challenged both in opening and in color. The sibling "color changer" seedling did not develop the rich morning color that it did on warmer days, and while there was a bit of color changing evident by late afternoon, it was nowhere near as dramatic as on sunny days. I am guessing this is both by way of less contrast (because the overall initial bloom color did not develop) and also because there was no sun today to burn off the surface pigment color. Ultimately that sibling may put on its best color changing display in warmer, or warmer night, areas.
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Another "good hair" day with a different bloom (5-13, the day after the bloom in the previous image; daytime highs and lows for our city, per Accuweather, were 73/53, 71/57, 70/53 on the 11th, 12th, and 13th, respectively).
Bloom today was not so good (5-22, daytime highs and lows for yesterday and today were (or were predicted to be) 63/52, 67/52).
Maybe this whole thing about CMOs is not so much about cool or cold temperatures the night before/early morning of the bloom, but cool or cold temperatures, in the 60s, on the previous
DAY?
It'd be nice if somebody could nail that down.
You asked about the parentage of this lemon seedling... check your Tree Mail. I hadn't actually measured the scape height, so I went out and checked; it appears to be about 18".
Maybe that might improve if the plant were actually in the ground somewhere, if I could find a suitable spot.
I know that plants "from the South" never achieve their registered bud count here. I am guessing that your "superior offspring" came about from good recessive genes.
Your observation on the relationship of scape height to siting is fascinating - that is not something that had ever occurred to me. Most of my garden gets a fair amount of shade. The daylilies with the most annoyingly stunted scapes are actually in my "full" (or as full as it gets) sun part of the garden. They are in sun from at least mid morning (if not earlier) until late afternoon or early evening (depending on the season). And that seedling (and its color changing sibling) are both sitting on my patio, which is right on the edge of that "full" sun area. Hmmm. (I don't think that I'm about to dig all of those daylilies and move them into shade... most of them do well enough, and one routinely exceeds its registration height. I am also beginning to suspect that water may have some role to play wrt the scape height, too. With all of the rain we had this past winter, I am seeing taller scapes on some of these daylilies than I have seen before.)
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ing, some one hand me a towel! 
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