I have the odd little grey hair around the sideburn area/ just above the ears.. I find they can be `stubborn`.... I just mix a little of my normal chemical-based hair colour and just draw it through/onto the grey specifically, ..the Back2natural is kind to your hair, especially the system hair, and gives a seamless blend [colour-wise] between your own and system in the event of a colour lift/change. This is inevitable as your system ages and from washings/UV-exposure etc.
Grey hair tends to be resistant. The Back2natural is very easy to use and good for the hair too.Hope that helps.. Paul.
ps.. I do my colouring with the system de-bonded... I can see my growing hair better that way.