Stalwart Apse Indigo
Stalwart Apse Indigo (#5D57F1) is a true blue with a neon character. It sits at the high-saturation edge of its family. Use it sparingly, as signage, accent, or highlight against darker surfaces. Its HSL profile (242°, 85%, 64%) places it in the highly saturated band at a mid lightness. Best used in small doses, like logos, CTAs, focus rings, or highlight text, where its saturation becomes a feature rather than noise. For a confident two-color system, pair it with its complementary yellow. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English stǣl-wyrðe, stable-and-worthy. As a color modifier, stalwart implies a saturated-and-loyal-and-firm quality where the hue carries the dependable-and-trustworthy visual presence of a Knight-Templar guard. Sits at the bold-and-firm end of the grid, parallel to steadfast and firm in usage.
Latin absis, vault / arch-recess. As a color modifier, apse implies a semicircular-vaulted-altar-end quality, the visual register of Romanesque-and-Byzantine-cathedral hand-laid mosaic-and-fresco-decorated semicircular altar-end vaulted-apse architectural surfaces under candle-and-incense apse light. Sits at the modifier-and-architecture end of the grid, parallel to nave and aisle in usage.
Indigofera tinctoria, the South Asian legume whose leaves yield the deep blue dye that has clothed humanity for at least four thousand years — Egyptian linen, Mayan textile, the slave-grown plantations of Carolina. The color refers to a freshly indigo-dyed cotton thread: a saturated, slightly violet-shifted deep blue with the slight lustre of a fiber surface oxidized in air. Deeper than cobalt, cooler than royal.
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.