Optical dot gain (light scattering or Yule–Nielsen effect) is an important effect influencing the quality of tone reproductions. Based on probability descriptions on the light scattering, a framework is established for describing this effect on the reflectance and color appearance of a chromatic halftone image. General expressions for the reflectance and CIEXYZ tristimulus values have been derived. Simulations for images printed with 2 inks have been carried out by applying Gaussian type of point spread function (PSF). Dependence of the optical dot gain on the optical properties of substrate and inks, the dot geometry etc., have been studied in detail.