This paper reviews the research progress in the preparation of blue, green, and red carbon dots (CDs) by carbonization, microwave, and water (solvent) thermal methods in recent years. The different properties of three-primary carbon dots prepared by different methods were analyzed. The main factors affecting the fluorescence color of CDs are summarized, including the types and concentrations of precursors, the types of reaction solvents, and the reaction temperature. The main challenges currently faced in the preparation of three primary color CDs are pointed out, and the potential solution to control the emission wavelength of CDs at 460 nm, 550 nm and 630 nm accurately is proposed. From the perspective of industrial application and intelligent response, the development direction of the series of fluorescent colors synthesized by the additive color method of three-primary CDs is prospected.