Dahlia (Dahlia variabilis, or D. pinnata) is one of the most popular garden and cut flowers around the world owing to its great variety of flower colors, sizes and shapes. Dahlia is an auto-allo-octoploid plant with 2n = 8x = 64, which enables enormous variation in many gene combinations, and more than 50,000 cultivars have been bred in the last century. This chapter summarizes recent research advances, with a focus on flower color and vase lifeVase life. The pigments that confer flower color in dahlia are flavonoidsFlavonoids: anthocyaninsAnthocyanin, flavonesFlavone and 6ʹ-deoxychalcones6'-Deoxychalcone. AnthocyaninsAnthocyanin and flavonesFlavone are common pigments found in many plant species, while 6ʹ-deoxychalcones6'-Deoxychalcone are found in a limited number of species. The amount and combination of pigments determine flower color. The first section describes the underlying molecular mechanisms of flower color. Findings from the recent publications about pigment biosynthetic genes, variegationVariegation and bicolorBicolor flower pattern formation are summarized, and at last, current schematic model for flower color breeding in dahlia is proposed. The second section summarizes breeding programs targeting vase lifeVase life elongation and the development of the long-vase-life cultivars ‘Eternity Torch’, ‘Eternity Romance’ and ‘Eternity Rouge’. Dahlias are known as short-vase-life cut flowers, so extending their vase lifeVase life increases their value. The process of development of new cultivars by cross-breeding is described. To improve the vase lifeVase life of dahlia flowers, cross-bred selections were conducted for five generations and promising offsprings with long vase lifeVase life were selected, from 2014 to 2021 using 22 commercial dahlia cultivars with large differences in vase lifeVase life as initial breeding materials.