Is it permissible to mix red henna with black katam and put it on the grey hair of the beard, noting that after that the colour of the beard will be black from a distance, and from close up it will be clear that the colour is dark brown?.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said:
The Sunnah is to change the grey hairs by using henna, or henna and katam. If it is changed using henna it will be orange and if it is changed using henna and katam it will be between red and black. There is nothing wrong with that and no sin involved, in sha Allah.