The result will depend on your natural hair colour and the percentage of white hairs. Choose a shade and see if it matches your natural colour.
If in doubt, make a hair strand test. If you like the result, proceed with entire hair colouring.
Choose a shade close to your natural hair colour: up to 2 shades lighter or darker than your current hair colour.
Since it is difficult to make an already dyed hair lighter, if this is the case with you, choose a darker shade.
If you are a darker or olive skin tone, try the warm brown shades of Kolora. The colder shades are more suited to a cold or pink skin tone.
The usual developing time of hair dye is 30 minutes and it ensures saturated colour result. For lighter shades and in case of stubborn grey hairs, you may extend the time up to 45 minutes in order to obtain more intense colour and even hair coverage.