Bumper Number Color(s)

[FRC2973]

Rule R15 states:....The numerals must be at least 4 inches high, at least in ¾-inch stroke width and in a contrasting color from its background....

The word color is singular in this rule; does this mean that the numbers can only be one solid color, or can a second color be used to help with the contrast - surrounding a white number with black or vice versa, for example - to make it more clearly visible?

[GDC]

Rule <R15> requires that the body of the number (the part that is ≥4 inches tall and with ≥3/4 inch stroke width) be of "a" (single) contrasting color. Adding small borders of a highly contrasting color around the external perimeter of the number for the purposes of increasing the contrast and clarity of the number would not violate the rule, as long as the addition of the contrasting border does not reduce the size or stroke width of the body of the number.