Errol Laborde, author of "Marched the Day God: A History of the Rex Organization", presented a theory that the colors were based on heraldry: all three colors correspond to a heraldic tincture, and Rex's goal may have been to create a tricolor to represent their "kingdom". Purple was widely associated with royalty, while white was already heavily used on other national flags, and was thus avoided. Furthermore, he noted that a flag in green, gold and purple in that order complies with the rule of tincture, which states that metals (gold or silver) can only be placed on or next to other colors, and that colors cannot be placed on or next to other colors.