Is drying of paint a chemical or a physical change?

This depends on the type of paint. In oil paint there is a physical change as volatile substances evaporate - and a chemical change as the paint hardens. In water-based paint (latex based) the paint loses water and so that part is a physical change - from wet to dry. But it also polymerizes (hardening, irreversible) which is chemical.

Only washable paint is physically drying by evaporation (reversible, otherwise it wouldn't be 'washable').