Also written 暈繝彩色. A method of coloring used in painting as well as for decorative motifs in crafts and architecture. Also known as graded shading danbokashi 段暈 because unlike the blending of ink or colors in shading, here distinct bands of color are placed next to each other in order to give the impression of shading. These bands of color then give the impression of a rainbow which led to the name *ungen 繧繝 (rainbow) saishiki (coloring). Sometimes one color of paint is applied in parallel bands from lighter to darker shades, from outside to inside. At other times, two contrasting colors, each of which shading from light to dark, are placed in bands next to each other in order to emphasize the effect of shading. If the gradations of color(s) move inversely from dark to light, from outside to inside, this is called opposite rainbow coloring, gyaku-ungen 逆繧繝.
The technique is believed to have been introduced to China from Central Asia. Some scholars have suggested that it may have been derived from mosaic or weaving color combinations used in the West. This originally was one attempt at a kind of shading which was common in China from the 5th-6th century, reaching its peak in the Tang dynasty. Ungenzaishiki, in the Tang dynasty, became stylized and four colors were consciously selected as sets for contrastive effect: the blues (*byakugun 白群, *gunjō 群青, and gunjō mixed with *sumi 墨), the greens (*byakuroku 白緑, *rokushō 緑青, and rokushō mixed with sumi), the reds (*tan 丹, *shu 朱, and shu mixed with sumi), and the purples (creating lighter and darker effects by mixing hakushoku ganryō 白色顔料 with sekishoku yūki ganryō 赤色有機顔料). When using two contrasting colors, the rule was usually to place blues next to reds and greens next to purples. What originally may have been an effort at conveying light and dark or even a sort of depth and three-dimensionality in painting through juxtaposition of light and dark color, soon transformed itself into a purely decorative device.
In Japan, in the 8th century, it was used as a decorative motif and used as well as in Buddhist art where it was often seen in floral scrolls. The multicolored lotus dais known as the kōinza 香印坐, found at the *Shōsōin 正倉院 repository, has geometric bands done in ungen zaishiki encircling fires and Buddhist deities. In architecture, one often finds this "rainbow coloring" effect used on floral or geometric motifs applied to offerings in the ceiling and on brackets, as can be seen in the ceiling of Byōdōin *Hōōdō 平等院鳳凰堂 in Kyoto, from the late Heian period when this coloring technique reached its peak.