Richeson Set of 20 Value Spectrum, Darks 1. The basic color divisions are separated into values from 1 (darkest dark) to 10 (lightest lights). The Value Spectrum sets allow the artist to focus on color temperature transitions because the value matching has already been done. Jack Richeson hand-rolled pigment-rich soft pastels offer luxurious texture and incredibly rich colors in an innovative size suitable for studio or plein air work. The set of 20 includes shades of Blue, Earth Red, Earth Green and Gray.