Band A depicts the lighter parts of the hair while band B shows the colours used for the dark hair. Note that 187 is the only colour used in both band A and band B. This is because the lighter colour in band A would weaken the stronger colours used in band B giving the final dark colour a muddy effect.
It is possible to add a little 199 black on top of the final colour of 177 if a deeper tone is required. The colour numbers are from the Faber-Castell Pastel Pencil range. See the full range of colours on our Colour Chart.