the colors blue and gray are recurrent throughout this novel. to what do they literally, and sometimes figuratively, refer?

Gray has a particular historical significance, as the uniforms of the Rebel army were gray. However, much like blue often relates not only to the literal color of the Union uniform but also to Henry's melancholy and brooding, Rebel gray also symbolizes the unknown of battle. The blue Union soldiers, who have been thinking about the implications of battle for days, are now faced with the enemy, both in the metaphor of the "blood-swollen god" of war and the Rebel army. The gray of smoke and fog symbolizes this unknown. Henry also has a relationship with nature and Crane uses elements of nature to communicate themes and character. These two metaphors coalesce in the grey fog of the battle. Henry and his regiment do not see the battle clearly; they see it in a haze. This shows their lack of knowledge. The haze and gray colors represent the unknown of battle and the detachment they have experienced thus far.