Iromuji (色無地 ) are a type of kimono without any colored patterns. They are of one solid color, which can not be black or white, as these have their own names and unique uses. Quite literally, the translation of Iromuji is “plain color”. They may sport woven patterns in the color of the kimono, but never of any other colors. Those woven jacquard patterns are called rinzu.
Iromuji kimono exist in any color, although most of the time subdued colors are used, which gives them a more mature and elegant vibe. Bright colors are connected to youth and more often found in kimono styles like the furisode.
Additionally they can have 0 to 5 family crests (so called mon), depending on their formality. Rather casual ones would have 0, while an iromuji with 5 crests would be considered highly formal.
Who wears them?
Iromuji can be worn by married and unmarried woman alike. Because of their “plainness”, they are more considered to be for older woman, who don’t want to attract too much attention, but rather underline their elegance and show an sophisticated attitude.
When are they used?
I wouldn’t go so far as to call them the official tea ceremony kimono, but they are a popular choice for this occasion, as a kimono for tea ceremony should not draw attention away from the ceremony itself. Without any patterns, their subdued colors and a fitting plain and simple obi, there is no other kimono more suitable for this. Other kimono like the homongi or furisode would be too much of a distraction.
Depending on the crests and used obi, they can be used for a wide range of events. They are acceptable for wedding parties (not for the bride!), graduation ceremonies (not for the graduate!) and other social events like parties, dinners or concerts (think more in the direction of a classical concert than AKB48).
Kimono Kanji 101
Iromuji いろむじ 色無地
色 = Iro = color
無地 = Muji = plain
綸子 = Rinzu = figured satin / jacquard pattern