Can a triyodashi tithi born under mrigashira nakshatra can wear blue sapphire because for Mars nakshatra born sir told to wear Neelam but for triyodashi tithi sir told that Saturn becomes bad

Can a triyodashi tithi born under mrigashira nakshatra can wear blue sapphire because for Mars nakshatra born sir told to wear Neelam but for triyodashi tithi sir told that Saturn becomes bad so wanted to get clarification on this