Hair is a feature that is not difficult to depict and often causes more anxiety than is necessary.
The first thing to remember is to simplify. It is the shape of the hair and the general light and dark areas that should be identified, rather than individual hairs. I usually start with a mid-tone to lay down basic tonal areas and the directional flow of the hair. Then, with this portrait, I applied cream and yellow ochre, before deepening the darks with dark umber and terracotta. As I progressed through the tonal values, I created more detail, whilst still avoiding the depiction of each and every hair.
At this stage, the hair is reaching completion, though the remaining stages will impact significantly on the final result. I will view the portrait from a distance to assess the overall shape of the hair, making sure that the shadowed areas are sufficient to create the illusion of depth to the spherical shape of the head. I will deepen the darks further and assess the need to lighten the lights. Once I am satisfied with the accuracy of the rendering, I will decide whether the final result is aesthetically pleasing. This stage involves artistic judgment, rather than referral to the original photo. It is often the case that photos can be improved in terms of colour, detail and lighting. I find this is especially true of hair which, like other features, changes colour dramatically, depending on the conditions. In my last portrait, I had to use artistic license to compensate for the darkness of the photo, as over-exposing the photo had meant a significant loss of detail and colour.
Drawing on coloured paper requires a different approach. In the earlier portrait of Joel, I applied the lights with pencils, instead of leaving the white of the paper to suggest the lights. As always with coloured pencil, preparation is important, as it is generally not possible to apply the palest of pigments on top of darker values.