Conversions, palettes, contrast & design ideas for this color.
Color profile
#40FC4A is a cool color from the Emerald family, closest in name to “Cathode Green”. In RGB it is rgb(64, 252, 74); in HSL, hsl(123, 97%, 62%).
The color Cathode Green, with hexadecimal code #40fc4a, resides within the green color family, the hue most connected to nature, growth, and renewal. Green soothes the eye more than any other color, making it ideal for wellness, sustainability, and financial brands. Additionally, it evokes emotions such as Nature, Healing, Balance, Stability and Calmness. Green is often linked to nature and growth universally, and in some cultures, it symbolizes fertility, renewal, and even immortality. In Islam, green holds significant religious meaning. With a high saturation of 97%, this color is intensely vivid—demanding attention and ideal for focal elements like buttons, banners, and brand marks. At 62% lightness, it strikes an approachable, open balance—bright enough to feel welcoming yet substantial enough to carry visual weight. This color is ideal for designs that aim to express Nature, Healing, Balance, Stability, or Calmness. 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
Cathode Green (#40FC4A) belongs to the Emerald 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.
Emerald green takes its name from the precious gemstone revered since at least 330 BC, when Cleopatra's emerald mines supplied the ancient world. Pantone named Emerald its Color of the Year for 2013, citing its associations with sophistication and renewal. Art Nouveau designers like Alphonse Mucha used emerald tones extensively, pairing them with gold to create their signature opulent aesthetic.
Emerald green conveys upscale elegance and is ideal for luxury brands, jewelry companies, and high-end hospitality. It pairs naturally with gold, brass, and cream for a rich, timeless palette. In web design, emerald buttons on a white background combine trust (green) with premium appeal.
Sitting on the cool side of the spectrum (hue 123°), it promotes a feeling of calm distance and intellectual clarity, which is why cool hues dominate corporate identities, healthcare design, and productivity tools. At 97% saturation, this is a highly vivid color that demands attention. Use it where maximum visual impact is needed—feature banners, accent buttons, and data-visualization highlights.
Emerald feels aspirational and abundant—it suggests growth coupled with achievement. Unlike casual greens, emerald carries an air of refinement that makes it suitable for formal invitations, gala events, and exclusive product lines.
At 62% lightness, it reads clearly on dark backgrounds and provides a welcoming, open feel in light-themed designs—versatile across both contexts.
Use emerald as a dark background for product photography, allowing gold or white products to shine. Combine emerald tiles with marble textures for luxury real-estate branding. In fashion e-commerce, emerald category headers signal the premium collection.
Every format
Every way to write Cathode Green — one-tap copy on every format; tap on any card to learn what it is and when to use it.
#40FC4A
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(64, 252, 74)
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(123, 97%, 62%)
HSL breaks a color into Hue, Saturation and Lightness — the most intuitive way to lighten, darken or mute a color in CSS.
hsv(123, 75%, 99%)
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(123 25% 1%)
HWB blends a pure hue with Whiteness and Blackness — a painter-friendly model added in CSS Color 4 for quick tints and shades.
cmyk(75%, 0%, 71%, 1%)
CMYK is the subtractive Cyan-Magenta-Yellow-Black ink model. Use these values when preparing artwork for a printer or commercial press.
oklch(86.75% 0.262 143.50)
OKLCH is a modern, perceptually-uniform space (Lightness, Chroma, Hue). It powers smooth gradients and accessible palettes in today’s CSS.
oklab(86.75% -0.210 0.156)
OKLab is the Cartesian form of OKLCH — ideal for blending and interpolating colors without the muddy midpoints older spaces produce.
L: 87.58, a: -77.62, b: 68.40
CIELAB is a device-independent, perceptually-uniform space. It is the standard for measuring color difference (ΔE) and matching across devices.
L: 87.58, C: 103.46, H: 138.61
LCH is CIELAB in cylindrical form — Lightness, Chroma and Hue — letting you adjust vividness and hue while staying perceptually even.
X: 38.16, Y: 71.21, Z: 18.21
CIE XYZ is the 1931 master space that underpins every other model here — the scientific bridge used to convert between color systems.
4258890
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 Cathode Green.
Percentages show each channel's share of the total light (R + G + B) in Cathode Green.
Ink coverage
Ink needed to reproduce Cathode Green 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 Cathode Green 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 Cathode Green — per-line copy, or grab the whole block.
background-color: #40FC4A;
color: #40FC4A;
border: 2px solid #40FC4A;
background-color: rgb(64, 252, 74);
background-color: hsl(123, 97%, 62%);
--color: #40FC4A;
Shades · light to dark
Lighter and darker steps of Cathode Green — 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 Cathode Green 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 #40FC4A — same mood, each with its own character.
Looking for more Green shades? Browse Green colors →
Inspiration
Curated Unsplash photos that carry the mood of Cathode Green — hover any tile to download it or view the original.
Good to know
Harmony