Countouring Tecniques is not only perfect for framing the face but also brilliant for showing off the structure of a hair cut. This is subtle way of highlight facial features and bring a hint of lightness arounbd the face. This and also be used to distinguish features of creative hair cut for example to make layers more prominent or to show off the length of the hair. This technique is not designed to drastically change the colour of the whole hair, just the parts you with to expose.
To archieve this effect first examine clients facial features and find out what the client ewould like to highlight, do thje same for hair cut then carful with you colour selection free hand coulour your sections making sure you create a natural blend towards the root area.