Cornwall is well known for having a wonderful clarity in its Light, this is reflected in many Cornish Paintings and is definately worth practicing over and over again with any subject whether a landscape, seascape or object, and where there is light there is shadow, i usually mix a thin coat of Ultramarine, crimson and a tad of Paynes grey in quite a diluted consistency for the shadow colour and for the light , sometimes adding instead of white to pick out highlights a very pale powder blue really stands out, experiment and see what suits you, but if a painting looks lifeless and flat , it’s usually because it is lacking in contrast.