答：界:=MA(CLOSE,27);

B买:IF(CROSS(指导线,界) OR CROSS(买线YGB,卖线YGB),C,DRAWNULL),COLORMAGENTA,NODRAW;

持仓:IF(买线YGB>=卖线YGB,C,DRAWNULL),COLORRED,NODRAW;

S卖:IF(CROSS(界,指导线) OR CROSS(卖线YGB,买线YGB),C,DRAWNULL),COLORLIGRAY,NODRAW;

空仓:IF(买线YGB<卖线YGB,C,DRAWNULL),COLORGREEN,NODRAW;