darken (
http://definr.com/darken)
v 1: become dark or darker; "The sky darkened" [ant:
brighten]
2: become or make darker; "The screen darkend"; "He darkened
the colors by adding brown" [syn:
dim] [ant:
brighten]
3: tarnish or stain: "a scandal that darkened the family's good
name"
4: make dark or darker; "darken a room" [ant:
brighten]