Dense Hollow Ruby
Dense Hollow Ruby (#A31021) is a true red with a jewel character. It carries the deep, saturated richness of a gemstone. Authoritative and slightly formal, it works well for type and heavy UI elements. Its HSL profile (353°, 82%, 35%) 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 teal. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin dēnsus, thick / crowded — sharing root with English condense. As a color modifier, dense implies a saturated-and-tightly-packed quality where the hue carries maximum pigmentation per visual unit-of-area. Sits at the bold-and-saturated end of the grid, parallel to thick and concentrated in usage.
Old English holh, hollow-place. As a color modifier, hollow implies a scooped-and-empty-and-resonant quality, the visual register of bell-and-gourd-and-tree-hollow hand-scooped-and-empty-and-resonant bell-and-gourd-and-tree-hollow hollowed-and-scooped-and-empty-and-resonant surfaces under bell-and-gourd-and-tree-hollow campanile-and-harvest-and-old-oak resonant-and-empty-light. Sits at the modifier-and-mood end of the grid, parallel to void and blank in usage.
From the Latin ruber — simply, red. The gemstone is a chromium-tinged corundum, harder than anything in nature except diamond, and so saturated that a fine Burmese pigeon's blood ruby at auction outpaces a comparable diamond by weight. The color borrows the gem's confidence: a clear, glassy red without the brown of garnet or the blue of crimson.
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.
Moderately saturated colors gain a small bump in P3 — the difference is usually visible side-by-side on wide-gamut hardware but won't change the character of the color.