Indigo has a long history in Japanese textiles and remains a recognizable cultural color, but one object cannot represent every regional technique or period. Natural dyeing produces variation through process and material.
A photograph should preserve that variation rather than forcing all blues toward one branded hue.
Find a real material reference
Photograph dyed cloth, workwear, a craft display, or another documented source where access is appropriate. Record maker, place, and lighting when available.
A blue sign or evening shadow may resemble indigo but should not be described as indigo dye.
Expose for texture and depth
Watch the blue channel and specular highlights on cloth. Soft directional light can reveal weave, repeated dyeing, wear, and folds.
Include a neutral or skin reference when the surrounding light is strongly colored.
Edit blue relationships
Set white balance before HSL. Separate cyan ambient light, painted blue, and dyed indigo instead of rotating them into one hue.
Review on a calibrated display when color accuracy matters and state that screen color is an interpretation of material color.
Sources and further reading
These references informed the cultural context in this field note.