Have you noticed how the chat text of some people is a different color?
How about those annoying gold-sellers, spaming text that you just can't
ignore until you blacklist them? Perhaps you are a party leader who wants
to issue clearly recognized instructions. Here's how to do it.
Basic format
Type in |H|h|cff{CSS color code, like FF0000 for red or 0000FF for blue}{message}|h
for example
|H|h|cffFF0000The world is a carousel of color.|h
Color Selection
The {CSS color code} is six hexadecimal-digits,
which allows over 16-million color combinations.
Here's a chart of hundreds of standard colors
http://herohog.com/CSScolorChart.html
If you like, create your very own unique color at
http://www.quackit.com/css/css_color_codes.cfm
Advanced Color Codes
You can CHANGE the color within the same message like this
Multi-colored: |H|h|cffFF0000red|h |H|h|cffFFFF00yellow|h |H|h|cff0000FFblue|h
That's all for now, because this is a
BASIC guide.
However, please post a comment if you know how to add
additional Special Effects like Blinking, Scrolling, Underlined,
italicized, or changing the BACKGROUND color.
Addons
There are probably Add-ons that will simplify the process for you.
I do not have any to recommend, but one place to check is at
http://curse.com/
Final WARNING
Over use of color will make you very, very unpopular.

Use these techniques
ONLY if you have a valid reason, which
is clearly understood by the people seeing your messages.