#66fd39
a balanced, electric green · neutral · closest name: Lime
At a glance
Every number on this page in one read: what #66fd39 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 | #66fd39 |
| RGB | rgb(102, 253, 57) |
| HSL | hsl(106, 98%, 61%) |
| CMYK | cmyk(60%, 0%, 78%, 1%) |
| LAB | lab(88.6 -72.1 75.2) |
| LCH | lch(88.6 104.2 133.8) |
| OKLCH | oklch(0.878 0.259 139.8) |
| Decimal | 6749497 |
| Display P3 | color(display-p3 0.400 0.992 0.224) |
Copy-ready code
/* CSS */
color: #66fd39;
background-color: #66fd39;
/* Tailwind (arbitrary) */
class="text-[#66fd39] bg-[#66fd39]"
/* SCSS */
$brand: #66fd39;
/* SwiftUI */
Color(red: 0.400, green: 0.992, blue: 0.224)
/* Android */
Color.parseColor("#66fd39")
/* Flutter */
Color(0xFF66FD39)
/* Python / OpenCV (BGR) */
(57, 253, 102)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. #66fd39 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: #F4FDF1;
--brand-100: #E9FCE3;
--brand-200: #CEFBC1;
--brand-300: #A9FE90;
--brand-400: #7EFD58;
--brand-500: #66fd39;
--brand-600: #3AF202;
--brand-700: #30CA02;
--brand-800: #26A202;
--brand-900: #1F7406;
--brand-950: #144904;
--brand: #66fd39;
--brand-ink: #000000;
}Colors that work with #66fd39
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 #66fd39
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 | #D039FD | Directly opposite — maximum tension | |
| Analogous left | #C8FD39 | Neighbour, quieter | |
| Analogous right | #39FD6E | Neighbour, quieter | |
| Split-complement 1 | #6E39FD | Contrast without the clash | |
| Split-complement 2 | #FD39C8 | Contrast without the clash | |
| Triadic 1 | #3966FD | Even thirds — balanced and loud | |
| Triadic 2 | #FD3966 | Even thirds — balanced and loud | |
| Tetradic | #39C8FD | Fourth corner of the square scheme |
RGB percentages
CMYK percentages
Color previews
#66fd39 text on a black background
contrast 15.67:1
#66fd39 text on a white background
contrast 1.34:1
CSS3 live lab
The quick brown fox
color: #66fd39;
background-color: #66fd39;
Glowing headline
text-shadow: 2px 2px 8px #66fd39;
Soft neon halo
text-shadow: 0 0 14px rgba(102, 253, 57, 0.45);
box-shadow: 0 12px 32px -8px rgba(102, 253, 57, 0.45);
border: 3px solid #66fd39; background: linear-gradient(135deg, #66fd39, #39FD8F);
Monochromatic scale
Palettes built from #66fd39
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: Lime (#00ff00) — ΔE2000 3 away, with its history, psychology and brand usage.
#66fd39 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.
#66fd39, answered
What color is #66fd39?
#66fd39 is a balanced electric green, closest to Lime (ΔE2000 3). It sits at 106° on the hue wheel with 98% saturation and 61% lightness, which reads as neutral.
What is the RGB value of #66fd39?
rgb(102, 253, 57) — 102 red, 253 green and 57 blue out of 255, or 40% / 99.2% / 22.4% by channel.
Is #66fd39 a light or a dark color?
It is a light color. Relative luminance is 0.7337 and perceived brightness is 79%, so black text on it reaches 15.67:1.
Should I use black or white text on #66fd39?
Black. It scores 15.67:1 against #66fd39, versus 1.34:1 for white — AAA at any size.
What is the complementary color of #66fd39?
#D039FD sits directly opposite on the wheel. Softer options are the split-complements #6E39FD and #FD39C8, which give the same contrast with far less vibration.
What colors go well with #66fd39?
For interface work: #F6FAF4 as the surface, #CAEDC0 for borders, #5D9B4B for secondary text, #9F37FF as an accent and #1E7E01 for hover and pressed states. For a palette, the analogous pair #C8FD39 and #39FD6E stays calm, while #D039FD is the loudest partner.
What is #66fd39 in CMYK for printing?
cmyk(60%, 0%, 78%, 1%). 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 #66fd39 warm or cool?
Neutral — it scores 57 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #AEFD39; nudged cooler, #37FF52.