My example, unfortunately, is a phalaenopsis, not a slipper, but the same concept applies.
I received a Phal. Pylo's Flame from Peter Lin at Big Leaf Orchids, and it bloomed last summer with a coppery color:
Here's the same plant right now (2 of the 3 spikes - last year's [above] returned one blossom this year, out of the frame):
I suspect the redder color is due to it forming earlier in the spring, rather than the heat of the summer.
I received a Phal. Pylo's Flame from Peter Lin at Big Leaf Orchids, and it bloomed last summer with a coppery color:
Here's the same plant right now (2 of the 3 spikes - last year's [above] returned one blossom this year, out of the frame):
I suspect the redder color is due to it forming earlier in the spring, rather than the heat of the summer.