The reaction would be:
CuSO4(aq) + NaOH(aq) = Cu(OH)2 (s) + Na2SO4(aq)
AS we can see from the equation a solid is formed therefore a precipitate is formed which is the copper (II) hydroxide which has a blue to purple appearance. This can be observed since copper (II) hydroxide has a low solubility in aqueous solution.