Shakkai is right. Variegation is generally affected by changes in growing conditions and environment. When a plant is stressed or under less than ideal conditions variegated plants will produce greener leaves....similar response to flowering less under similar changes.
Variegation in orchids always amazes me, physiologically it is so stressful on the plant. It's like being in flower all the time, and then when you consider the conditions that orchids grow under in the wild....wow.
Cheers.
Jim
I didn't know variegation was stressful for orchids!
What growing care can be given to minimize the stress. . .keep them growing steady and strong?