The below information is from the ABA rulebook regarding numbers and number plates. Colored plates are not allowed unless earned. Only the sanctioned colored plates are to be used for riders whom have earned plates.
When in doubt solid 3" black letters on a white black plate is the norm for district. Not blue, not purple or other random colors.
This information can be location in the current ABA rulebook under section "X Rider identification" and reads as follows:
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A rider’s current earned or ABA issued number must appear on that rider’s number plate during all competition. This identification can appear in the following forms only:
a) District number—solid black number (minimum 3” high) on a white background.
b) National Age Group (NAG) number—solid black number, #1-10 on a light gray background.
c) Overall National number—solid white number, #1-99 on a black background.
d) Elite number—solid black number (minimum 3” high) on a white background.
e) Junior number—solid white number (minimum 3” high) on a black background.
f) Redline Cup number—solid black #1 -3 on a yellow background.
g) Race of Champions number—solid white #1 on a red background.
*Any rider not using his/her earned number may not be scored for that race.
