color explorer · sRGB · CIE · Crayola
Everything here is computed locally in one HTML file — no network, no storage, no dependencies. The address bar keeps the current palette and color, so a link is shareable.
Why the gray background? Perceived color depends heavily on what surrounds it. The stage defaults to an 18% neutral gray, the standard surround for judging color; the swatch top-left in the header switches it to white, dark gray or black so you can watch a color shift without changing.
Palettes. CSS/X11 names are exact. Crayola values are the widely circulated approximations of crayon pigment, grouped by the assortment each name shipped in. The xkcd set is the raw result of a public naming survey, so it is opinion rather than standard. The web-safe, xterm-256, CGA, spectral, blackbody and OKLCh sets are generated from their definitions rather than transcribed.
Color science. Conversions use the sRGB D65 matrices, CIE Lab/LCh, and Ottosson's OKLab/OKLCh. Contrast is reported as both WCAG 2 ratio and APCA Lc (0.1.9 constants). Correlated color temperature uses McCamy's cubic approximation; the Planckian locus is integrated from Planck's law against the CIE 1931 2-degree observer, which keeps it honest below 1667 K where the usual spline fits stop being defined. Dominant wavelength and purity are measured from D65 through the color to the spectral locus.
Gamut triangles are built at runtime from each space's primary chromaticities, so the diagram is derived, not drawn from memory.