Conversions, palettes, contrast & design ideas for this color.
Color profile
#1F4BB7 is a cool color from the Blue family, closest in name to “Once in a Blue Moon”. In RGB it is rgb(31, 75, 183); in HSL, hsl(223, 71%, 42%).
The color Once in a Blue Moon, with hexadecimal code #1f4bb7, 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 Trust, Peace, Loyalty, Integrity and Tranquility. 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 71% saturation, this color is clearly chromatic yet balanced—colorful enough to be distinctive without overwhelming adjacent content. With a mid-range lightness of 42%, it offers excellent versatility—readable as text on light backgrounds and visible as an element on dark ones. This color is ideal for designs that aim to express Trust, Peace, Loyalty, Integrity, or Tranquility. 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
Once in a Blue Moon (#1F4BB7) belongs to the Blue 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.
Blue's scarcity in nature made it a late addition to human color vocabulary—Homer's 'wine-dark sea' notably omits the word blue entirely. The breakthrough came with Egyptian Blue (~2200 BC) and later ultramarine from Afghan lapis lazuli, which Medieval artists hoarded for divine subjects. Synthetic ultramarine (1826) and cobalt blue democratized the color, enabling Impressionists like Monet and Renoir to paint blue-drenched landscapes affordably.
Blue is the most universally liked color and dominates corporate branding (Facebook, LinkedIn, IBM, Samsung). Use it to establish trust, competence, and professionalism. Lighter blues suit wellness and social apps, while darker blues convey authority and security. Avoid using blue for food branding—it suppresses appetite.
Sitting on the cool side of the spectrum (hue 223°), it promotes a feeling of calm distance and intellectual clarity, which is why cool hues dominate corporate identities, healthcare design, and productivity tools. With 71% saturation, it occupies a comfortable middle ground: colorful enough to be distinctive, yet restrained enough for extended reading or large surface areas.
Blue lowers blood pressure and heart rate, promoting calm and focused thought. It signals reliability and integrity, which is why it is the default choice for banks, insurance companies, and government institutions. In UX, blue links and buttons feel intuitive because users have been trained by decades of web convention.
With a mid-range lightness of 42%, 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.
Pair classic blue (#0047AB) with warm amber for a nautical or heritage brand. Use gradient blues (light-to-dark, top-to-bottom) for app onboarding screens that feel expansive and inviting. In data dashboards, blue is the safest primary chart color—it's distinct, professional, and colorblind-friendly.
Every format
Every way to write Once in a Blue Moon — one-tap copy on every format; tap on any card to learn what it is and when to use it.
#1F4BB7
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(31, 75, 183)
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(223, 71%, 42%)
HSL breaks a color into Hue, Saturation and Lightness — the most intuitive way to lighten, darken or mute a color in CSS.
hsv(223, 83%, 72%)
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(223 12% 28%)
HWB blends a pure hue with Whiteness and Blackness — a painter-friendly model added in CSS Color 4 for quick tints and shades.
cmyk(83%, 59%, 0%, 28%)
CMYK is the subtractive Cyan-Magenta-Yellow-Black ink model. Use these values when preparing artwork for a printer or commercial press.
oklch(45.34% 0.178 263.84)
OKLCH is a modern, perceptually-uniform space (Lightness, Chroma, Hue). It powers smooth gradients and accessible palettes in today’s CSS.
oklab(45.34% -0.019 -0.177)
OKLab is the Cartesian form of OKLCH — ideal for blending and interpolating colors without the muddy midpoints older spaces produce.
L: 35.48, a: 26.31, b: -61.17
CIELAB is a device-independent, perceptually-uniform space. It is the standard for measuring color difference (ΔE) and matching across devices.
L: 35.48, C: 66.59, H: 293.27
LCH is CIELAB in cylindrical form — Lightness, Chroma and Hue — letting you adjust vividness and hue while staying perceptually even.
X: 11.63, Y: 8.74, Z: 45.87
CIE XYZ is the 1931 master space that underpins every other model here — the scientific bridge used to convert between color systems.
2050999
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 Once in a Blue Moon.
Percentages show each channel's share of the total light (R + G + B) in Once in a Blue Moon.
Ink coverage
Ink needed to reproduce Once in a Blue Moon in four-color print. Heaviest ink: Cyan.
Print tip: treat these values as a starting point — final output depends on printer profile, paper stock and calibration.
Accessibility · WCAG
How bright Once in a Blue Moon 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 Once in a Blue Moon — per-line copy, or grab the whole block.
background-color: #1F4BB7;
color: #1F4BB7;
border: 2px solid #1F4BB7;
background-color: rgb(31, 75, 183);
background-color: hsl(223, 71%, 42%);
--color: #1F4BB7;
Shades · light to dark
Lighter and darker steps of Once in a Blue Moon — 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 Once in a Blue Moon 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 #1F4BB7 — same mood, each with its own character.
Looking for more Blue shades? Browse Blue colors →
Inspiration
Curated Unsplash photos that carry the mood of Once in a Blue Moon — hover any tile to download it or view the original.
Good to know
Harmony