Conversions, palettes, contrast & design ideas for this color.
Color profile
#37313B is a neutral color from the Charcoal family, closest in name to “Professor Plum”. In RGB it is rgb(55, 49, 59); in HSL, hsl(276, 9%, 21%).
The color Professor Plum, with hexadecimal code #37313b, belongs to the charcoal family—a deep, warm neutral softer than black. Charcoal tones lend authority and understated elegance to any composition. Additionally, it evokes emotions such as Luxury, Royalty, Spirituality, Imagination and Wisdom. With negligible saturation (9%), this color is effectively achromatic—a pure neutral that pairs with any hue without competition. Its low lightness of 21% 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
Professor Plum (#37313B) belongs to the Charcoal color family.
As an achromatic shade, this color carries a timeless, versatile neutrality that anchors any palette it joins.
Charcoal, the drawing medium, has been used since prehistoric cave art at Lascaux and Altamira—making it one of humanity's oldest creative tools. As a color, deep charcoal became fashionable in Victorian-era menswear and later in mid-century modern furniture upholstery, where it provided a softer alternative to stark black.
Charcoal is an excellent substitute for pure black in typography and backgrounds—it feels warmer and reduces eye strain on screens. Dark-mode interfaces frequently use charcoal (#222–#333) rather than true black (#000) to avoid OLED screen smearing and to soften contrast.
Charcoal communicates authority and gravitas without the starkness of black. It suggests understated confidence, making it ideal for luxury brands, law firms, and editorial publications that want sophistication without drama.
Its low lightness of 21% gives it a deep, intense presence. Deep tones like this excel as dark-mode backgrounds, header bars, and anywhere a sense of gravity or luxury is desired.
Use charcoal as a dark-mode background paired with crisp white text and a single vivid accent (electric blue, lime green, or coral). For print, charcoal paper stock with metallic foil stamping creates tactile, premium business cards and invitations.
Every format
Every way to write Professor Plum — one-tap copy on every format; tap on any card to learn what it is and when to use it.
#37313B
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(55, 49, 59)
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(276, 9%, 21%)
HSL breaks a color into Hue, Saturation and Lightness — the most intuitive way to lighten, darken or mute a color in CSS.
hsv(276, 17%, 23%)
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(276 19% 77%)
HWB blends a pure hue with Whiteness and Blackness — a painter-friendly model added in CSS Color 4 for quick tints and shades.
cmyk(7%, 17%, 0%, 77%)
CMYK is the subtractive Cyan-Magenta-Yellow-Black ink model. Use these values when preparing artwork for a printer or commercial press.
oklch(32.34% 0.019 311.92)
OKLCH is a modern, perceptually-uniform space (Lightness, Chroma, Hue). It powers smooth gradients and accessible palettes in today’s CSS.
oklab(32.34% 0.013 -0.014)
OKLab is the Cartesian form of OKLCH — ideal for blending and interpolating colors without the muddy midpoints older spaces produce.
L: 21.30, a: 4.99, b: -5.33
CIELAB is a device-independent, perceptually-uniform space. It is the standard for measuring color difference (ΔE) and matching across devices.
L: 21.30, C: 7.30, H: 313.10
LCH is CIELAB in cylindrical form — Lightness, Chroma and Hue — letting you adjust vividness and hue while staying perceptually even.
X: 3.46, Y: 3.32, Z: 4.60
CIE XYZ is the 1931 master space that underpins every other model here — the scientific bridge used to convert between color systems.
3617083
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 Professor Plum.
Percentages show each channel's share of the total light (R + G + B) in Professor Plum.
Ink coverage
Ink needed to reproduce Professor Plum in four-color print. Heaviest ink: Key (Black).
Print tip: treat these values as a starting point — final output depends on printer profile, paper stock and calibration.
Accessibility · WCAG
How bright Professor Plum 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 Professor Plum — per-line copy, or grab the whole block.
background-color: #37313B;
color: #37313B;
border: 2px solid #37313B;
background-color: rgb(55, 49, 59);
background-color: hsl(276, 9%, 21%);
--color: #37313B;
Shades · light to dark
Lighter and darker steps of Professor Plum — 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 Professor Plum 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 #37313B — same mood, each with its own character.
Looking for more Charcoal shades? Browse Charcoal colors →
Inspiration
Curated Unsplash photos that carry the mood of Professor Plum — hover any tile to download it or view the original.
Good to know
Harmony