A named color for indigo.
藍色 (Ai-iro) is catalogued here as indigo. Aizome indigo dye tradition with well-documented historical usage; indigo colorant studies exist but no per-record physical-sample measurement is attached, so HEX is a screen approximation, not direct sRGB colorimetry.
Tobunken records the underlying color/material term in the Nara-period vocabulary database derived from 『大日本古文書』; this supports historical name attestation, not measured sRGB.
Conservation-science studies publish spectral/reflectance evidence for the related pigment or dye family. This supports the material context, not a per-record measurement; the displayed HEX remains a digital approximation.
Name appears in at least one CC BY-SA Wikipedia traditional Japanese color list; HEX remains a Chroma Cathay digital approximation for design use.
Traditional color names predate modern screen color spaces, so this HEX value is a design approximation rather than a material measurement.