A series of colloidal CdSe quantum dots (QDs) were synthesized, and the photoluminescence (PL) quantum yield of CdSe nanocrystals was found to increase at first and then decrease with increasing size. The chromatic coordinates of samples with different size and different size distributions were calculated to see the influence of size distribution of CdSe QDs. And white QDs sample was prepared by mixing red and blue QDs. The experimental value of chromatic coordinates of the prepared sample coincide with that estimated according to the empirical formula.