A well-known, if extremely rough, convention in the world of color measurement says that in CIEL*a*b* or CIEL*C*h space, a dE* value of less than one indicates that two colors are visually indistinguishable to the human eye. The reality is far more complex than this. The limits of visual perception actually differ depending upon which portion of color space is being discussed.
Automotive interiors are comprised of a variety of materials and produced by several companies. To achieve a uniform appearance, automotive companies have tight quality control (QC) tolerances. Color tolerances are typically ±0.5 for ΔL*, Δa*, Δb* and gloss tolerances are typically ±0.3 to 0.5 gloss units (GU).