Conversions, palettes, contrast & design ideas for this color.
Color profile
#421B99 is a cool color from the Indigo family, closest in name to “Gentian Blue”. In RGB it is rgb(66, 27, 153); in HSL, hsl(259, 70%, 35%).
The color Gentian Blue, with hexadecimal code #421b99, belongs to the blue color family, the world's most universally preferred hue. Blue projects trust, stability, and intellectual calm, which is why it dominates corporate, financial, and technology branding worldwide. Additionally, it evokes emotions such as Luxury, Royalty, Spirituality, Imagination and Wisdom. Blue signifies tranquility and stability. In Middle Eastern cultures, it can also represent protection against the evil eye, while in Western cultures, it symbolizes calmness and reliability. At 70% saturation, this color is clearly chromatic yet balanced—colorful enough to be distinctive without overwhelming adjacent content. Its low lightness of 35% produces a deep, rich appearance—conveying gravity and luxury, particularly effective in dark-mode designs and premium packaging. This color is ideal for designs that aim to express Luxury, Royalty, Spirituality, Imagination, or Wisdom. It can be effectively used in web design, branding, and marketing materials to attract attention and convey specific messages.
Key facts
The story of this color
Gentian Blue (#421B99) belongs to the Indigo color family.
This vivid mid-tone strikes the ideal balance between intensity and readability, making it a strong candidate for primary brand colors, interactive UI elements, and logo design where immediate recognition is essential.
Indigo dye—extracted from Indigofera plants—has been used for over 6,000 years, with the oldest known samples found in Peru. It was the foundation of the blue-dye trade across India, West Africa, and the Americas, and its economic importance rivaled that of spices. Levi Strauss chose indigo-dyed denim for the first blue jeans in 1873, cementing indigo's place in everyday fashion worldwide.
Indigo occupies the territory between blue and purple, lending depth without purple's flamboyance. It is excellent for evening-event branding, high-end fashion, and editorial design. Pair indigo with soft gold or warm white for a sophisticated contrast, or with coral for a contemporary editorial palette.
Sitting on the cool side of the spectrum (hue 259°), it promotes a feeling of calm distance and intellectual clarity, which is why cool hues dominate corporate identities, healthcare design, and productivity tools. With 70% saturation, it occupies a comfortable middle ground: colorful enough to be distinctive, yet restrained enough for extended reading or large surface areas.
Indigo conveys depth, wisdom, and introspection. It carries the trustworthiness of blue with a hint of purple's creativity, appealing to brands that want to appear both reliable and imaginative—think higher education, think-tanks, and creative consultancies.
With a mid-range lightness of 35%, this tone is highly versatile: dark enough to serve as body text on white, yet light enough to stand out on charcoal or navy backgrounds.
Use indigo as a full-page background with centered white text for impactful statement pages. Combine indigo with copper accents for a rich, modern luxury feel in packaging. In web design, indigo sidebar navigation with white icons creates a polished, app-like interface.
Every format
Every way to write Gentian Blue — one-tap copy on every format; tap on any card to learn what it is and when to use it.
#421B99
Hexadecimal is the web’s universal color notation — two digits each for red, green and blue. Drop it straight into HTML, CSS or any design tool.
rgb(66, 27, 153)
RGB is the additive Red-Green-Blue model every screen uses to emit light. The default choice for websites, apps and on-screen UI.
hsl(259, 70%, 35%)
HSL breaks a color into Hue, Saturation and Lightness — the most intuitive way to lighten, darken or mute a color in CSS.
hsv(259, 82%, 60%)
HSV (also called HSB) maps Hue, Saturation and Value/Brightness. It is the model behind the color pickers in Photoshop, Figma and most design apps.
hwb(259 11% 40%)
HWB blends a pure hue with Whiteness and Blackness — a painter-friendly model added in CSS Color 4 for quick tints and shades.
cmyk(57%, 82%, 0%, 40%)
CMYK is the subtractive Cyan-Magenta-Yellow-Black ink model. Use these values when preparing artwork for a printer or commercial press.
oklch(37.08% 0.185 287.61)
OKLCH is a modern, perceptually-uniform space (Lightness, Chroma, Hue). It powers smooth gradients and accessible palettes in today’s CSS.
oklab(37.08% 0.056 -0.176)
OKLab is the Cartesian form of OKLCH — ideal for blending and interpolating colors without the muddy midpoints older spaces produce.
L: 24.46, a: 48.23, b: -61.13
CIELAB is a device-independent, perceptually-uniform space. It is the standard for measuring color difference (ΔE) and matching across devices.
L: 24.46, C: 77.87, H: 308.28
LCH is CIELAB in cylindrical form — Lightness, Chroma and Hue — letting you adjust vividness and hue while staying perceptually even.
X: 8.39, Y: 4.24, Z: 30.51
CIE XYZ is the 1931 master space that underpins every other model here — the scientific bridge used to convert between color systems.
4332441
The 24-bit integer value of the color — handy for databases, APIs, game engines and low-level graphics code.
Channel breakdown
How much red, green and blue light mixes into Gentian Blue.
Percentages show each channel's share of the total light (R + G + B) in Gentian Blue.
Ink coverage
Ink needed to reproduce Gentian Blue in four-color print. Heaviest ink: Magenta.
Print tip: treat these values as a starting point — final output depends on printer profile, paper stock and calibration.
Accessibility · WCAG
How bright Gentian Blue is, and how far black and white text clear each WCAG bar.
Contrast ratio · 1:1 → 21:1 (log scale)
Developer shortcuts
Copy-and-paste CSS for Gentian Blue — per-line copy, or grab the whole block.
background-color: #421B99;
color: #421B99;
border: 2px solid #421B99;
background-color: rgb(66, 27, 153);
background-color: hsl(259, 70%, 35%);
--color: #421B99;
Shades · light to dark
Lighter and darker steps of Gentian Blue — the color's full brightness range in one strip.
The dot marks the original color. Hover any shade to copy its hex or open its color page.
Harmony · 180° apart
Two colors opposite on the wheel — maximum contrast for attention-grabbing accents.
The dot marks the original color. Hover any shade to copy its hex or open its color page.
Harmony · adjacent hues
Neighboring hues on the wheel — harmonious, calm combinations that feel unified.
The dot marks the original color. Hover any shade to copy its hex or open its color page.
Harmony · 120° apart
Three colors evenly spaced on the wheel — vibrant and energetic, yet balanced.
The dot marks the original color. Hover any shade to copy its hex or open its color page.
Harmony · 90° apart
Four colors evenly spaced on the wheel (tetradic) — rich schemes with multiple accents.
The dot marks the original color. Hover any shade to copy its hex or open its color page.
Accessibility
How Gentian Blue reads across five kinds of color vision — a ✓ Friendly verdict means the color difference stays distinguishable for that vision type.
The dot marks the original color. Hover any shade to copy its hex.
Harmony overview
The lead color from each harmony scheme, side by side — a shortcut to the full palettes above.
Perceptually nearby
A step away in brightness, richness or shade — each still feels like the same color.
From the color-name library
The closest named colors to #421B99 — same mood, each with its own character.
Looking for more Blue shades? Browse Blue colors →
Inspiration
Curated Unsplash photos that carry the mood of Gentian Blue — hover any tile to download it or view the original.
Good to know
Harmony