Light of Christ means in the bible: Although the Bible does not contain the phrase “light of Christ”, the principles which apply it are often mentioned. This exact phrase can be found in Alma 28.14, Moro. DC 88.7. The Bible phrases “spirit” and “light” can sometimes be used interchangeably with the word “light” in the same sentence. See John 1:14-8:12. Sometimes, however “spirit” is used to refer to the Holy Ghost. Therefore it should not always be taken as referring to Christ’s light.
(in Bible Dictionary)