Bluedifference

Bluedifference is a term used in color science to describe the portion of a color difference that arises from contrasts along the blue–yellow axis. It is not a standard official metric, but rather a way to discuss how much two colors differ specifically in their blue and yellow content within perceptual color spaces.

In perceptual color spaces that include a blue–yellow component, such as CIELAB where the b* coordinate encodes the blue–yellow axis, bluedifference can be represented as the difference in that axis between two colors. For colors with coordinates (L1*, a1*, b1*) and (L2*, a2*, b2*), the bluedifference can be defined as Δb* = |b1* − b2*|. In broader practice, bluedifference may be considered as a component of a full color-difference measure, sometimes used with normalization or weighting to account for luminance (L*) or chroma.

Applications of the concept include color quality control, branding and product color matching, and image or film workflows where blue hues are particularly important. By isolating the blue–yellow component, practitioners can diagnose whether color shifts are primarily due to blue content and adjust processes accordingly.

Limitations include the fact that color perception is multi-dimensional and influenced by lighting, surrounding colors, and observer variation. Relying solely on bluedifference can misrepresent overall perceptual differences, so it is typically used as a supplementary descriptor alongside full color-difference metrics such as ΔE. Related concepts include the b* axis in CIELAB, overall color difference (ΔE), and other color-space components used in color management.