Pastel painting is the simplest and purest method of painting using pure color without the addition of medium - essentially, pastels are transparent watercolors. The advantage is that the painting does not suffer the effects of age caused by changes in the medium as in other methods such as oils. One disadvantage is its relative fragility, although if framed under glass and given normal care work paintings will stand the test of age as proven in Master paintings which have survived for 200+ years with their brilliant colors untouched by the years.
The keys to mixing pigments and achieving exactly the color you wanted is dependent on having a basic knowledge of color theory and experience - regardless of the medium you use for painting.
