void setColor(int start, int end, ColorRGBA color) {
        LetterQuad cursor = head.getNext();
        while (!cursor.isTail()) {
            if (cursor.getIndex() >= start && cursor.getIndex() < end) {
                cursor.setColor(color);
            }
            cursor = cursor.getNext();
        }
    }
@param start start index to set style. inclusive.
@param end   end index to set style. EXCLUSIVE.
@param color
jme3-core/src/main/java/com/jme3/font/Letters.java