What is an Alba Flower? Where Flower Colour Variations Come From

The phalaenopsis bellina "Fire" x sib bloomed! Because this is a special flower I decided to make a feature video for it to explain what it is that makes it special.
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Growing environment:
Indoors
Temperatures 18 - 33°C
Humidity 10 - 50%
South-west facing window
Morges, Switzerland
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Instagram: @marissakoopman