When you colour your hair to hide the grey, of course you want to cover up any grey roots as quickly as possible, especially if your grey hair tends to grow in fast.
Highlights and full colour
If you do a single process colour over your entire head of hair, you should normally go in for colouring about every six weeks. If you get highlights, you should normally plan on applying your highlights every two to four months. Colouring your hair too often can damage your hair due to all the chemicals in the colouring.
Touch-up tricks for grey hair
If your hair colour fades and the grey starts to show through, try a colour shampoo, which will give your colouring a boost. If your hair is light and your grey roots are starting to come, find a facial powder as close as possible to your hair colour and apply it directly to your roots to hide the grey. If your hair is dark, apply eyebrow pencil to the grey hairs at the roots.
Hair mascara for grey hair
Hair mascara is a simple and cost-effective way to hide those grey hairs that come in between colourings. Choose the colour closest to your regular hair dye colour and apply it with a wand just as you would mascara for your eyelashes. It will keep the grey covered until you wash or wet your hair.