Q:

What is the meaning of "casket grey" in this sentence?

I read a sentence in a chapter named "Discovering Tut: the saga continues":

Dark bellied clouds had scudded across the desert sky all day and now
  were veiling the stars in casket grey.

Casket means a chest or any rectangular box.
But I'm not able to figure out the context in which it has been used.

A:

Compare the expressions "sky blue", "lily white", "blood red".
A colour that follows a noun, particularly a noun that indicates a material (or at least visible) object, indicates that it is the colour of that object.

