Q.acidanthera peacock orchids
The first year there was purple in the middle of the bloom. The second and third year there was yellow. Why the change?
Peacock orchids come in flower colors ranging from white to a very rich, dark maroon red.
Peacock orchids require full sunlight, at least six hours a day, although they may tolerate some afternoon shade. Soil should be mildly acidic with a pH of 6.1 to neutral 7.0. Amending soil with peat moss provides excellent drainage as well as the slightly acidic soil conditions the plant prefers. Keep soil slightly moist at all times. Most gardeners rely upon rainfall to water peacock orchids.
Many of these orchids are sold in color assortments. This may be the case in your plants.
https://www.gardeningknowhow.com/ornamental/bulbs/peacock-orchid/growing-peacock-orchids.htm