Some suggestions from L'Oreal PARIS site on choosing and using hair colours.
How to choose a hair colour?
While choosing a hair colour, one should stay close to their natural hair colour. A successful hair colour is one that enhances a person's eyes, skin and actual hair texture and most of all, a colour that cares about hair condition through nourishing care.
How to avoid the hair colour from running down your face?
To avoid the colour running down your face, clean away any excess product from your skin with cotton wool or a sponge.
How often would you recommend colouring your hair at home?
It all depends on the colour you are using and the condition of your hair. The colour of the roots is also crucial: are they grey, or very different from the colour of the ends? Every 3 to 6 weeks on average is normal.