private void verifyColor(short color) {
		if ((color != BLACK) &&
				(color != RED) &&
				(color != GREEN) &&
				(color != YELLOW) &&
				(color != BLUE) &&
				(color != MAGENTA) &&
				(color != CYAN) &&
				(color != WHITE)) {
			throw new IllegalArgumentException ("Unknown color:" + color);
		}
	}