At first it looked like reference numbers, but as I looked again and changed one and recompiled on my test box, its the color...
Code:
Message(13,"Your target is too far away, get closer!");
changing to
Code:
Message(15,"Your target is too far away, get closer!");
where changing from 13 to 15, changes the output from red to yellow.
Like when you do #emote zone 15 TEXTHERE makes yellow: TEXTHERE. I'm assuming that the X = 15 in that case.