Chestnut Flanked White (CFW for short) causes the body colour of the bird to lose or almost lose colour.
This is a sex-linked recessive mutation.
There are two different CFW mutations, one red-eyed and one black-eyed.
The two mutations are multiple alleles, with the black-eyed dominating over the red-eyed.
The black-eyed was the first to appear. They usually have clear white backs/wings, but often with a few grey shadows.
The red-eyed have pale cream backs and rarely any shadows. Their black markings are usually better than those of the black-eyed.
A Chestnut Flanked White male
The continental standards that I know of call for light cream back and wings, so the red-eyed variety is prefered for showing.