There are many common expressions to describe unhealthy skin using colors (eg, , , ), but is not something in common use in modern Japanese. is commonly associated with pale and anemic skins, but is usually associated with jaundice (due to some liver disease). And according to Wikipedia, this guy () had intestinal tuberculosis, which rarely causes jaundice. I'm at a loss to explain this further, but we can instantly understand that his hand had a "very unusual and unhealthy-looking color", anyway.
Should this have been translated literally as "blue and yellow" rather than "ashen"? I'm not very sure, but "blue and yellow" seems a bit too vivid to my inner eyes... After reading the first part of (available here), somehow I feel the author was trying to describe something more colorless, -ish skin by ...