Balayage is a colour technique in which light blond colour accents are applied using a sweeping technique and therefore differs from the highlights applied with films. The result is that the colours contrast less hard with the natural hair colour than with the foil technique whereby you can see clear lines.
A Balayage can be applied directly to undyed hair from colour level 6 (dark blonde) with hair dye. For a natural color level 5 (light brown) to 2 (dark brown) I use the balayage technique as a pre-bleaching method that needs to be coloured with a second color treatment in the desired shade.
If your hair has already been dyed, I can never get a cool blonde colour in a single treatment with the Balayage colour technique and I have to achieve the desired result with foil techniques, which must then be dyed with a second colour treatment in the desired shade.