In the wedding costume, it is presumed that in the first half of the 18th century, a format was established in which uchikake (outer garment) of white ground, red ground and black ground were sequentially changed on white aigi (inner garment). Although these kinds of uchikake were given auspicious pattern regardless of the ground color, there is a blue uchikake which represents a pattern very similar to these, as a group. This article attempts to verify that such work is a wedding costume worn the fourth after the black one.In Japan, the word "Ao"(blue) has etymologically been closely related to "Kuro"(black) , "Aka"(red) and "Shiro"(white), but on the other hand "Ao"(blue) is in an incidental position for these three colors, so even in wed...