One example we see. Cooling night time temperatures will do this:
You can observe where the cool air flow is occuring, in this instance.
For the above, this stem was protected from the cool temperature by an overlapping leaf. There are more obvious examples to be had though I’d need to look through the photos. As time progresses with the cool nights, the leaves will continue to deepen with colorful hues.
We’ve had the same genetics not produce any color at harvest but when the nighttime temperature remains moderate. There has been no accounting for other variables, such as nutrition, that may encourage the change in color. This is fall nearing harvest.