http://forums.d2jsp.org/topic.php?t=36872318&f=34or you can use hex codes like.
Hello world!Code
[color=#FF0000]H[/color][color=#E90015]e[/color][color=#D4002A]l[/color][color=#BF003F]l[/color][color=#AA0055]o[/color] [color=#7F007F]w[/color][color=#6A0094]o[/color][color=#5500AA]r[/color][color=#3F00BF]l[/color][color=#2A00D4]d[/color][color=#1500E9]![/color]