Tested with Minecraft 1.3.2 on CraftBukkit 1.3.1-R2.0

Colors:

BLACK
WHITE
DARK_AQUA
AQUA
RED
BLUE
DARK_PURPLE
DARK_BLUE
DARK_GRAY
DARK_RED
GOLD
GRAY
GREEN
LIGHT_PURPLE
YELLOW

Other:

BOLD
ITALIC
UNDERLINE
STRIKETHROUGH
MAGIC
COLOR_CHAR
RESET