Different drying rates occur in oil paints because each individual pigment reacts diffently when mixed with the oil. Typically, oil paint is pigment mixed with linseed oil which actually oxidizes rather than evaporates.
Examples of fast drying oil paints ( approximately 2 days) are as follows:
Cobalt blue, Prussian blue, Raw Sienna, Raw Umber, Burnt Umber and Flake White
Examples of medium drying oil paints (approximately 5-6 days) are as follows:
All Cobalt violets, and greens, Sap green, Cerulean blue.
Examples of slow drying oil paints ( approximately 6-10 days) are as follows:
Alizarin Crimson, French Ultramarine, Lamp Black, Ivory Black, Titanuim white, Cadmium colours.