Nucleation and growth of two-dimensional (2D) islands on a terrace are the dominant growth mechanisms of colloidal crystals whose particle interaction is attractive. The step velocity, vstep, of the 2D islands at various area fractions, φarea, and polymer concentrations, Cp, has been investigated. At low Cp (weak attractive interaction between particles), there is a nearly linear relationship between vstep and φarea, whereas it is parabolic for high Cp (strong attraction). Depending on the Cp, two manners of kink generation at a step are observed: 1D nucleation under strong attraction and association of mound formation under weak attraction. As a result of mound formation, abundant kinks are created at steps, resulting in a linear relationship between vstep and φarea, whereas the relationship is parabolic for step propagation associated with 1D nucleation. Though the kink site is the most favored site for particles to be incorporated into crystals, weak attractive interaction makes the step front site an incorporation site as well, and this latter process is the main mechanism for mound formation. This study is the first to elucidate the relationship between step kinetics and the kink generation mechanism of colloidal crystals, and these new findings significantly contribute to better control of the growth of colloidal crystals.