#a3ef21
a balanced, electric green · neutral · closest name: Green Yellow
At a glance
Every number on this page in one read: what #a3ef21 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 | #a3ef21 |
| RGB | rgb(163, 239, 33) |
| HSL | hsl(82, 87%, 53%) |
| CMYK | cmyk(32%, 0%, 86%, 6%) |
| LAB | lab(86.8 -49.9 80.2) |
| LCH | lch(86.8 94.5 121.9) |
| OKLCH | oklch(0.870 0.225 129.5) |
| Decimal | 10743585 |
| Display P3 | color(display-p3 0.639 0.937 0.129) |
Copy-ready code
/* CSS */
color: #a3ef21;
background-color: #a3ef21;
/* Tailwind (arbitrary) */
class="text-[#a3ef21] bg-[#a3ef21]"
/* SCSS */
$brand: #a3ef21;
/* SwiftUI */
Color(red: 0.639, green: 0.937, blue: 0.129)
/* Android */
Color.parseColor("#a3ef21")
/* Flutter */
Color(0xFFA3EF21)
/* Python / OpenCV (BGR) */
(33, 239, 163)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. #a3ef21 is pinned to step 500; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.
:root {
--brand-50: #F9FDF2;
--brand-100: #F2FAE5;
--brand-200: #E5F7C4;
--brand-300: #D4F796;
--brand-400: #BEF462;
--brand-500: #a3ef21;
--brand-600: #96E410;
--brand-700: #7DBE0E;
--brand-800: #64980B;
--brand-900: #4A6E0C;
--brand-950: #2E4508;
--brand: #a3ef21;
--brand-ink: #000000;
}Colors that work with #a3ef21
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 #a3ef21
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 | #6D21EF | Directly opposite — maximum tension | |
| Analogous left | #EFD421 | Neighbour, quieter | |
| Analogous right | #3CEF21 | Neighbour, quieter | |
| Split-complement 1 | #213CEF | Contrast without the clash | |
| Split-complement 2 | #D421EF | Contrast without the clash | |
| Triadic 1 | #21A3EF | Even thirds — balanced and loud | |
| Triadic 2 | #EF21A3 | Even thirds — balanced and loud | |
| Tetradic | #21EFD4 | Fourth corner of the square scheme |
RGB percentages
CMYK percentages
Color previews
#a3ef21 text on a black background
contrast 14.93:1
#a3ef21 text on a white background
contrast 1.41:1
CSS3 live lab
The quick brown fox
color: #a3ef21;
background-color: #a3ef21;
Glowing headline
text-shadow: 2px 2px 8px #a3ef21;
Soft neon halo
text-shadow: 0 0 14px rgba(163, 239, 33, 0.45);
box-shadow: 0 12px 32px -8px rgba(163, 239, 33, 0.45);
border: 3px solid #a3ef21; background: linear-gradient(135deg, #a3ef21, #21EF28);
Monochromatic scale
Palettes built from #a3ef21
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: Spring Bud (#a7fc00) — ΔE2000 2.9 away, with its history, psychology and brand usage.
#a3ef21 in the real world
Where a color in this family tends to land, and the interface roles it is usually asked to play.
Sits outside most CMYK gamuts — expect a duller press result, or specify a spot ink.
#a3ef21, answered
What color is #a3ef21?
#a3ef21 is a balanced electric green, closest to Green Yellow (ΔE2000 3.3). It sits at 82° on the hue wheel with 87% saturation and 53% lightness, which reads as neutral.
What is the RGB value of #a3ef21?
rgb(163, 239, 33) — 163 red, 239 green and 33 blue out of 255, or 63.9% / 93.7% / 12.9% by channel.
Is #a3ef21 a light or a dark color?
It is a light color. Relative luminance is 0.6963 and perceived brightness is 80%, so black text on it reaches 14.93:1.
Should I use black or white text on #a3ef21?
Black. It scores 14.93:1 against #a3ef21, versus 1.41:1 for white — AAA at any size.
What is the complementary color of #a3ef21?
#6D21EF sits directly opposite on the wheel. Softer options are the split-complements #213CEF and #D421EF, which give the same contrast with far less vibration.
What colors go well with #a3ef21?
For interface work: #F8FAF4 as the surface, #DCEDC0 for borders, #7D9B4B for secondary text, #361CF4 as an accent and #4E7709 for hover and pressed states. For a palette, the analogous pair #EFD421 and #3CEF21 stays calm, while #6D21EF is the loudest partner.
What is #a3ef21 in CMYK for printing?
cmyk(32%, 0%, 86%, 6%). This is a screen-to-ink approximation — a color this saturated sits outside most CMYK gamuts and will print duller than it looks here.
Is #a3ef21 warm or cool?
Neutral — it scores 43 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #EFEF21; nudged cooler, #56F11E.