what theeory does the narrator suggest about colors?

"The book is made up mainly of striking, simple images, like colors. Death associates the death of others by a certain colour depending on the sky. Hans Hubermann's eyes are described as being made of silver, which look right into you, and is often referred to by the way he plays the accordion. Rosa Hubermann is said to have a cardboard complexion with a wardrobe figure and elasticy hair. Max Vandenburg has hair like feathers (or twigs when it isn't washed). Rudy Steiner has lemon coloured hair. Liesel herself is characterised through words rather than imagery, perhaps reflecting her love of words and earning her the title "the book thief"."