Primary Tiěhuī
Primary Tiěhuī (#170D33) is a deep indigo with a cool character. It leans cool, sitting on the blue, green, and violet side of the wheel. Quiet and dependable, a fit for product UI and data visualization. Its HSL profile (256°, 59%, 13%) places it in the balanced band at a dark lightness. It works well as a headline, icon, or deep background in an otherwise light layout, pairing cleanly with cream, bone, and warm neutrals. For a confident two-color system, pair it with its complementary lime. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin prīmārius, first — adjectival suffix -ary, derived from prīmus (first). As a color modifier, primary implies a neutral-and-foundational-and-base-color quality where the hue carries the visual register of Bauhaus-and-Mondrian-De-Stijl foundational-primary-color theoretical-color-system. Sits at the neutral-and-foundational end of the grid, parallel to primal and foundational in usage.
Chinese 铁灰, iron-gray — the formal Chinese color name for the metallic-iron-gray of tiěqì cast-iron and tiěqī iron-lacquer. Tiěhuī color refers to a Qing-dynasty tiěqī-coated wooden box: a dark cool-gray with the metallic finish of multi-coat iron-tannin lacquer on hand-shaved cypress. Slightly warmer than Hēihuī (black-gray).
Closest matches
The nearest named color in three reference sources, ranked by perceptual distance (ΔE76 in CIELAB). ΔE < 1 is imperceptible to most viewers; ΔE > 10 is clearly different. When two sources point to the same hex they’re merged into one tile; click any to open that color’s page.
Variations
Click any swatch to exploreHarmonies
Accessibility
How this color appears to viewers with the four major color-vision-deficiency types. Computed via the Machado (2009) physiologically-based model. If a tile matches the original, the color reads the same to that viewer.
The color used as foreground text against pure white and pure black, with the contrast ratio and WCAG 2.1 grade. Aim for AA (4.5:1) for body text and AA Large (3:1) for 18 pt+ headlines; AAA (7:1) is the gold standard for long-form reading surfaces.
Wide gamut
The CSS Color 4 wide-gamut form of this color. Both swatches render the same color on every display — the P3 form only diverges from sRGB when a designer pushes channels outside sRGB's reach.
This color sits well within the sRGB cube. P3 and sRGB share the gray axis and most desaturated tones, so a P3 display renders this identically to an sRGB display.