Smoldering Niagara
Smoldering Niagara (#004FC7) is a true azure 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 (216°, 100%, 39%) 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 amber. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
The progressive participle of smolder, to burn slowly without flame. Used as a color word since the late nineteenth century for the deep reds and oranges of barely-flame coal — the warm saturated darks where the heat is internal rather than emitted. Sits in the bold-and-warm corner, slightly less luminous than burning and slightly less calm than rich.
The triple waterfall on the Niagara River between New York and Ontario — the largest waterfall by flow rate east of the Mississippi. Niagara blue refers to the color of the water as it falls: a saturated, slightly green-shifted deep blue with the optical complexity of glacial-melt water mixed with limestone-derived calcium carbonate. Cooler than turquoise, deeper than aqua, with the natural-wonder weight of a falls visited by millions annually.
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 is chromatic enough that authoring it as P3 native (instead of clamping to sRGB) gives a perceptibly more saturated render on wide-gamut displays — modern Macs, iPhones, iPads, and most recent OLED laptops.