Roman Numerals:
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV
or, just write out the words in place of color or numerals:
ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE, TEN, ELEVEN,
TWELVE, THIRTEEN, FOURTEEN, FIFTEEN
plus, of course, CUE BALL.