From SA-MP Wiki
~l~Black (lower case L)
~h~Turn text color lighter (used too much will make your text white, doesn't work on black)
Special Text Letters
~u~up arrow (gray)
~d~down arrow (gray)
~<~left arrow (gray)
~>~right arrow (gray)
]displays a * symbol (Only in text styles 3, 4 and 5)
~k~keyboard key mapping (e.g.
~k~~PED_FIREWEAPON~). Look here for a list of keys
|Be careful, using too many text colors or special characters in one gametext may crash every player the gametext is shown to. Additionally, avoid using an uneven usage of the ~ character.
Example: ~~r~Hello, ~g~how are ~y~~you?~