Most heroes these days have receding hair line and are going for hair transplantation. When in the movie business, the hair undergoes a lot of chemical and other treatments that require immense care.
If there is no proper protection, stress too accelerates in hair fall for these artistes. Other artistes have greying hair as a problem. They need to colour it regularly. It could be genetic.
Take for instance Vijay Devarakonda, he has quite a bit of grey hair and if you have the Yellandu episode in World Famous Lover, you can clear see his grey hair. People tend to think that it is dust because he works in coal mines, but Vijay had the luxury of keeping it natural during the shoot.
Also, for all the three roles, he took quite a lot of care in hair styling to look different for the three characters.