I stumbled upon this thread after reading some information about Eternity on the official wiki — I must say I’m disappointed with it, even after the modifications on 9/3/2013. At the very least, the developer(s) responsible for designing this weapon should consider adding the bursts of light / darkness which occur when drawing sunrise and twilight, their respective throwing animations, and a mystic forge recipe to break it down into its subcomponents should the wielder decide to pursue a new signature appearance.
However, like many of the posters above me, I would prefer an overhaul of Eternity’s coloration to closely match the op’s suggestion (a conglomeration of day and night, though perhaps with slightly less purple). In practice, it should be an item which inspires jealousy amongst players who only possess 1 of the 2 requisite legendary weapons (like me).