Why is this Poinsettia White

I snapped this photo years ago (maybe three years back). I like photographing objects that are different. I consider this different because I am used to a poinsettia that is red. This is white. Well, the more interesting thing is that when I went back to this park on a December, the same plant has now red flowers (technically, its not the flowers. The red portion are actually leaves. The "flowers" are its young foliage). 

So, why is it white then? I was reading some references online and learn that it must be kept in an ambient temperature of less than sixty degrees Fahrenheit for it to maintain its red colors. So now, I know why poinsettias are red on chilly December months.