The filmmaker revealed that he intends to remove any grey before shooting commences on Student of the Year.
Johar posted on Twitter: "So I start Student of the Year 2mor... I am about to colour my hair and cover my greys... to match up to the youth on set!! (sic)"
The college-themed project features debut actors Siddharth Malhotra, Varun Dhawan and Alia Bhatt.
Bhatt shared her first-day apprehension in a tweet to director-father Mahesh Bhatt, saying: "I'm scared. I suddenly can't remember anything anyone said to me."
Johar's first day of shooting started with a song sequence directed by Farah Khan.
Student of the Year is the 39-year-old's fifth production as a director.
The movie, which Johar finished writing in New York, is the first of his releases not to feature Shah Rukh Khan.