I use 6 pencils when doing sepia pictures in Pastel Pencils. The key colour I use is Brown Ochre (182 in the Faber Castell Pitt Pastel Pencil Range). The difference with this colour is that you can’t just water it down as you would with watercolour. You therefore have 6 pencils acting as different tones. Also with watercolour, I use white coloured paper but with Pastel Pencil work I use Sand Coloured Paper. I choose to start with putting ivory as a base colour onto the sand colour and work on top of that with the six pencils.
The pencils I use are: 103, 182, 180, 280, 175 and 199 (from the faber castell range). Those of you familiar with the colour numbers will know that 199 is black. Black I don’t use as a solid colour but a darkening agent when sometimes you need that bit extra. If you didn’t include black then you would lose out on that really strong dark contrast.