Abstract The maximal degree of polarization (DOP) for the visible solar light scattered by an aqueous droplet at a given scattering angle is found in this paper. Based on the Lorenz–Mie theory, the numerical expression for the DOP of the light scattered by any spherical particle is deduced. For the given scattering angle and aqueous droplet, the DOP dependent on wavelength is calculated according to familiar solar spectral colors. The maximal DOP of each spectral color is exhibited and some analyses are given. This analysis may contribute to applications of indicating atmospheric conditions and polarized light compass navigation.