Monocotman: It is also the low temperature. As I mentioned above, it is BOTH low temp and lack of chlorophyll. Even when it is covered with aluminimum foil, but if you don't meet the low temp requirement, the colour won't be correct either.
TyroneGenade: C. goeringii is a seasonal orchid so it has 4 conditions throughout the year (1 condition for every season). So, watering, lighting, and temperature are adjusted accordingly to the changing season. It is very hard to explain. However, here is the temperature requirement:
Spring and fall: 15C-19C (intermediate)
Summer: 25C-30C (hot to warm)
Winter: 0C-10C (cold)
C. goeringii is NOT a flexible orchid like many other orchids. The changing seasonal conditions must be met; otherwise, it will not do well for you. The temperature range stated above must be strictly followed (ie. no higher or lower). In Asia, the temperature goes up and down slowly throughout the year like a staircase. My Japanese Cymbidium vendor told me tha the lowest C. goeringii subsp. goeringii can go is -5C.