As an important ornamental plant, Bougainvillea spectabilis has many colors but lacks the rare blue color. In order to select a suitable host of genetic transformation that would be suitable for the exclusive accumulation of flavonoid pigment by absorbing dihydromyricetin (DHM) and the resulting color change toward blue, we carried out in vitro induction culture experiment on the Bougainvillea bracts of 6 varieties of red, white, yellow and purple with 4 common colors; The changes of color parameters and pigment content of bracts were measured after induction culture, and the correlation was analyzed. The result showed that：(1) the red green phase value (a^*) of bracts is the main color parameter that determines the color of bracts. Its color is mainly determined by beet pigment and flavonoid pigment, and betacyanins has the greatest influence. (2) Except that the content of flavonoids in the bracts of white varieties is higher than that of betacyanins, the content of beet pigment in the bracts of other varieties shows an upward trend, and the content of flavonoids pigment shows a downward trend. (3) The content of betalain is significantly positively correlated with the a^* value and negatively correlated with the b^* value of bracts，and the content of total flavonoids is significantly positively correlated with b^* value and extremely significantly negatively correlated with a^* value of bracts. (4) After being fed and cultured in vitro by DHM, the content and proportion of total flavonoids in the bracts of four varieties (‘Singapore White’, ‘Baolao Cheng’, ‘Chinese Beauty’, ‘Ratana Yellow’) increased significantly, and which of total beet pigment in the bracts of all varieties decreased. The increase of total flavonoids content in the bracts of ‘Singapore White’ (+65.77%) is the largest, and its change of content proportion (26.91%) is also the largest among the six varieties. (5) Through the comprehensive analysis of grey correlation degree, the white variety ‘Singapore White’ has the highest correlation degree (0.744 4) with the reference variety proposed by grey correlation degree analysis. Based on the results， Singapore White was the most appropriate transgene host for blue Bougainvillea ssp. The results of this study provide a reference for the directed breeding of blue Bougainvillea ssp..