From the wiki:
Color the character will be drawn with. If the most significant byte is not 0 then this color will be ignored (default) and the lightmap (if present) and scene brightness will be used for the tint of the character. Otherwise the three lower bytes are used for the tint the character will be drawn with. The least significant byte specifies red, then green and the third byte specifies blue. E.g. with 0xFF0000 the character would be drawn with a blue light.
Characters["character_name"].CharacterTint = 0xFF0000 -- blue tint