#51c921
a balanced, vivid green · neutral · closest name: Lime Green
At a glance
Every number on this page in one read: what #51c921 is made of, how bright it looks, and which way it leans.
Reads neutral. Warm and cool siblings keep the same lightness, so you can swap one in without redoing your contrast maths.
Every format
| HEX | #51c921 |
| RGB | rgb(81, 201, 33) |
| HSL | hsl(103, 72%, 46%) |
| CMYK | cmyk(60%, 0%, 84%, 21%) |
| LAB | lab(72.0 -60.8 66.0) |
| LCH | lch(72.0 89.7 132.7) |
| OKLCH | oklch(0.739 0.222 139.1) |
| Decimal | 5359905 |
| Display P3 | color(display-p3 0.318 0.788 0.129) |
Copy-ready code
/* CSS */
color: #51c921;
background-color: #51c921;
/* Tailwind (arbitrary) */
class="text-[#51c921] bg-[#51c921]"
/* SCSS */
$brand: #51c921;
/* SwiftUI */
Color(red: 0.318, green: 0.788, blue: 0.129)
/* Android */
Color.parseColor("#51c921")
/* Flutter */
Color(0xFF51C921)
/* Python / OpenCV (BGR) */
(33, 201, 81)Best text color
Only one of black and white can be right. This is the one, with the number that proves it.
Accessibility — WCAG contrast
Color scale — 50 to 950
A Tailwind-shaped ramp built around this exact hex. #51c921 is pinned to step 600; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.
:root {
--brand-50: #F6FCF3;
--brand-100: #ECF8E7;
--brand-200: #D5F3C9;
--brand-300: #B6EF9F;
--brand-400: #91E76E;
--brand-500: #6CDF3E;
--brand-600: #51c921;
--brand-700: #47AF1D;
--brand-800: #388C17;
--brand-900: #2C6615;
--brand-950: #1B400D;
--brand: #51c921;
--brand-ink: #000000;
}Colors that work with #51c921
Not a palette — a role sheet. Each swatch answers one question you will hit while building the component.
Surface, border, heading and body all derive from this one hue, so the screen stays coherent without a second palette.
Lightness flips, hue holds. The accent stays the anchor in both themes.
How to use #51c921
Derived from its contrast, chroma and lightness — not from taste.
- ✓Text and icons on dark surfaces
- ✓Primary buttons and calls to action
- ✓Focus rings, active and selected states
- ✓Brand accents, badges and data highlights
- ⚠Text of any size on white — fails WCAG AA
- ⚠Full-page backgrounds — tiring over long sessions
- ⚠Pairing with a same-lightness hue — edges vibrate
Similar colors
One move away from this hex in each direction. Every swatch is its own page.
Color relationships
The wheel positions with their names attached, so you can grab the one you actually need.
| Complementary | #9921C9 | Directly opposite — maximum tension | |
| Analogous left | #A5C921 | Neighbour, quieter | |
| Analogous right | #21C945 | Neighbour, quieter | |
| Split-complement 1 | #4521C9 | Contrast without the clash | |
| Split-complement 2 | #C921A5 | Contrast without the clash | |
| Triadic 1 | #2151C9 | Even thirds — balanced and loud | |
| Triadic 2 | #C92151 | Even thirds — balanced and loud | |
| Tetradic | #21A5C9 | Fourth corner of the square scheme |
RGB percentages
CMYK percentages
Color previews
#51c921 text on a black background
contrast 9.73:1
#51c921 text on a white background
contrast 2.16:1
CSS3 live lab
The quick brown fox
color: #51c921;
background-color: #51c921;
Glowing headline
text-shadow: 2px 2px 8px #51c921;
Soft neon halo
text-shadow: 0 0 14px rgba(81, 201, 33, 0.45);
box-shadow: 0 12px 32px -8px rgba(81, 201, 33, 0.45);
border: 3px solid #51c921; background: linear-gradient(135deg, #51c921, #21C961);
Monochromatic scale
Palettes built from #51c921
Shades — darker
Tints — lighter
Color harmonies
Nearest named colors
Ranked with CIEDE2000 across all 139 CSS keywords. Under ΔE 2 the eye stops telling them apart; over ΔE 10 they are plainly different colors.
Closest color with a full write-up: Pistachio (#93c572) — ΔE2000 10.4 away, with its history, psychology and brand usage.
#51c921 in the real world
Where a color in this family tends to land, and the interface roles it is usually asked to play.
Converts to four-color process without much drama. Proof it anyway.
#51c921, answered
What color is #51c921?
#51c921 is a balanced vivid green, closest to Lime Green (ΔE2000 2.8). It sits at 103° on the hue wheel with 72% saturation and 46% lightness, which reads as neutral.
What is the RGB value of #51c921?
rgb(81, 201, 33) — 81 red, 201 green and 33 blue out of 255, or 31.8% / 78.8% / 12.9% by channel.
Is #51c921 a light or a dark color?
It is a mid-tone. Relative luminance is 0.4363 and perceived brightness is 63%, so black text on it reaches 9.73:1.
Should I use black or white text on #51c921?
Black. It scores 9.73:1 against #51c921, versus 2.16:1 for white — AAA at any size.
What is the complementary color of #51c921?
#9921C9 sits directly opposite on the wheel. Softer options are the split-complements #4521C9 and #C921A5, which give the same contrast with far less vibration.
What colors go well with #51c921?
For interface work: #F6FAF4 as the surface, #CDEDC0 for borders, #619B4B for secondary text, #6F1CCE as an accent and #2C6E12 for hover and pressed states. For a palette, the analogous pair #A5C921 and #21C945 stays calm, while #9921C9 is the loudest partner.
What is #51c921 in CMYK for printing?
cmyk(60%, 0%, 84%, 21%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.
Is #51c921 warm or cool?
Neutral — it scores 55 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #8FC921; nudged cooler, #1FCB2D.