Hello here! I really wonder what does a phrase "to go white in face" mean?
Is it really getting paler and paler? Or is it turning red? Well should be a weird one but maybe you could help me. I've seen it in this context: "Mr Gloop was absolutely right. For suddenly there was a shriek, and then a splash, and into the river went Augustus Gloop, and in one second he had disappeared under the brown surface.
'Save him!' screamed Mrs Gloop, going white in the face". Yup, it is Roald Dahl's "Charlie and Chocolate factory".

Question

Hello here! I really wonder what does a phrase  "to go white in face" mean?
Is it really getting paler and paler? Or is it turning red? Well should be a weird one but maybe you could help me. I've seen it in this context: "Mr Gloop was absolutely right. For suddenly there was a shriek, and then a splash, and into the river went Augustus Gloop, and in one second he had disappeared under the brown surface.
'Save him!' screamed Mrs Gloop, going white in the face". Yup, it is Roald Dahl's "Charlie and Chocolate factory".

Answer

Hello,

If someone 'goes white in the face', then they are very scared and their face becomes paler. In frightening situations, adrenaline is released which then prepares you for a 'flight or flight' response to the situation. A white face is caused because there is reduced blood flow to the surface of the body. 
Blood is pumped to other areas of the body instead such as  arms, legs, shoulders, brain, eyes, ears and nose.

Answer

I would add that it's a common idiom meaning "extreme fright" That's what Dahl is describing here.
Now I see that Alexandra said this.