Difference Between Watercolour and Pastel Pencil

We were recently sent this email which gave us an opportunity to talk about one of the main differences between using Watercolour and using Pastel Pencils.William wrote in:

"Could I ask Colin some advice. Another member asked the colour of dogs noses in pastel I gave her the colours in watercolour as a mix of perm red & raw umber for pink, and burnt sienna & ultramarine for the black. I used sienna because it showed up in the coat and the eyes.Would the advice have been correct? In anticipation of the results."

Painting in watercolour does require mixing colours together to get the right results and the colours suggested would be great.However, pastel pencils do not necessarily need the watercolour techniques as we can use less colours to achieve good results and if too many colours are applied then there is a danger of over application and it is possible to overload the paper.What would work here is building up the nose base colours and carefully adding the colours suggested at that stage. I often do this myself if the references warrant it.