In this picture, a lot of the white is overexposed. There is some white along the sides that maintained proper exposure, but generally speaking, if you can't see individual scales, then you probably over exposed. That does not mean that this snake isn't white. It just means that this picture is not the best example that could be offered.
In this pic, there are two other sources of white. One is from the paper under the tub, and the other is from the fabric inside the tub. If the light was casting an odd color temp onto the subjects, wouldn't the other two whites behave in a similar manner?
I don't have any good imaging software here at work, so I can't put my cursor over any given pixel to find out it's true color. I can't tell for sure, but it does not look to me like the white's are even remotely similar given the different response I see from them in the image. The cloth is behaving more like the snake with regards to a color shift, but the paper under the tub is not. the paper that is seen outside the tub in the upper right has more of a color cast to me as well.
That being said, none of the known white in that image is acting quite like the snake's head is. There is a clear greenish tint seen on the snake's head which is absent from the other white in the image. The snake's white also changes as you go down the snake. Lighting and shadows likely has somehting to do with this effect, but I am not 100% certain that this is a white balance issue due to color temperature.
One final thing...the camera was likely set to auto-white-balance. It did the best job it could with the white in that image. If there is more than one light source however, then the image can really take on different color tones. If you have incanedscent lighting in a lamp, and also use a flash, you are now introducing two different colors of light, and many cameras can't compensate for this. I have seen images where the left side of the wall is mainly lit by the room lighting, and the wall behind the subject was lit mainly by flash. The color of the wall behind the person looks like it changes...
This is my input into this thread for now...maybe you are both correct...lol...