You need to learn about ANSI colour codes. You can find codes in your /etc/DIR_COLOR file.
Then you need to put them in your motd file. You cannot just type them in though...they are non-printing escape sequences. You would do something like this:
[user@box]$ echo -en "\033[1;34m" > /etc/motd
[user@box]$ echo "Text of your motd file....." >> /etc/motd
[user@box]$ echo -en "\033[0m" >> /etc/motd
If you ran 'cat /etc/motd' this would produce something like:
Text of your motd file.....
The first line puts the beginning escape sequence into the file, in this case...a nice dark blue. BE CAREFUL...as this will overwrite whatever is currently in the file, make sure you back it up first.
The second line is the actuall content of your motd file. You can break it up over multiple lines if you want, just press enter to get a new line BEFORE the closing quote. When you are happy with the layout then type the ' " >> /etc/motd ' bit. Notice that you use the >> redirection operator this time as to append to the motd file, so that your escape sequence isn't overwritten. You could also open the motd file in your favorite editor at this point, and type in your message that way...just dont edit the escape sequence, which will look like this: ^[[0;34m then save the file and complete step three...
The last line closes the colour escape sequence so everything goes back to normal after reading the file.