#40bc9b
a balanced, vivid cyan · cool · closest name: Medium Aqua Marine
At a glance
Every number on this page in one read: what #40bc9b is made of, how bright it looks, and which way it leans.
Reads cool. Warm and cool siblings keep the same lightness, so you can swap one in without redoing your contrast maths.
Every format
| HEX | #40bc9b |
| RGB | rgb(64, 188, 155) |
| HSL | hsl(164, 49%, 49%) |
| CMYK | cmyk(66%, 0%, 18%, 26%) |
| LAB | lab(69.0 -42.0 6.8) |
| LCH | lch(69.0 42.5 170.8) |
| OKLCH | oklch(0.718 0.119 171.7) |
| Decimal | 4242587 |
| Display P3 | color(display-p3 0.251 0.737 0.608) |
Copy-ready code
/* CSS */
color: #40bc9b;
background-color: #40bc9b;
/* Tailwind (arbitrary) */
class="text-[#40bc9b] bg-[#40bc9b]"
/* SCSS */
$brand: #40bc9b;
/* SwiftUI */
Color(red: 0.251, green: 0.737, blue: 0.608)
/* Android */
Color.parseColor("#40bc9b")
/* Flutter */
Color(0xFF40BC9B)
/* Python / OpenCV (BGR) */
(155, 188, 64)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. #40bc9b 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: #F4FAF9;
--brand-100: #EAF6F2;
--brand-200: #CFECE5;
--brand-300: #ABE3D4;
--brand-400: #81D4BE;
--brand-500: #58C6A9;
--brand-600: #40bc9b;
--brand-700: #34987D;
--brand-800: #297A64;
--brand-900: #21594A;
--brand-950: #15382E;
--brand: #40bc9b;
--brand-ink: #000000;
}Colors that work with #40bc9b
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 #40bc9b
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
- ⚠Thin strokes and 1px borders — they disappear on light UI
- ⚠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 | #BC4061 | Directly opposite — maximum tension | |
| Analogous left | #40BC5D | Neighbour, quieter | |
| Analogous right | #409FBC | Neighbour, quieter | |
| Split-complement 1 | #BC409F | Contrast without the clash | |
| Split-complement 2 | #BC5D40 | Contrast without the clash | |
| Triadic 1 | #9B40BC | Even thirds — balanced and loud | |
| Triadic 2 | #BC9B40 | Even thirds — balanced and loud | |
| Tetradic | #5D40BC | Fourth corner of the square scheme |
RGB percentages
CMYK percentages
Color previews
#40bc9b text on a black background
contrast 8.88:1
#40bc9b text on a white background
contrast 2.36:1
CSS3 live lab
The quick brown fox
color: #40bc9b;
background-color: #40bc9b;
Glowing headline
text-shadow: 2px 2px 8px #40bc9b;
Soft neon halo
text-shadow: 0 0 14px rgba(64, 188, 155, 0.45);
box-shadow: 0 12px 32px -8px rgba(64, 188, 155, 0.45);
border: 3px solid #40bc9b; background: linear-gradient(135deg, #40bc9b, #408ABC);
Monochromatic scale
Palettes built from #40bc9b
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: Jade (#00a86b) — ΔE2000 10 away, with its history, psychology and brand usage.
#40bc9b 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.
#40bc9b, answered
What color is #40bc9b?
#40bc9b is a balanced vivid cyan, closest to Medium Aqua Marine (ΔE2000 5.3). It sits at 164° on the hue wheel with 49% saturation and 49% lightness, which reads as cool.
What is the RGB value of #40bc9b?
rgb(64, 188, 155) — 64 red, 188 green and 155 blue out of 255, or 25.1% / 73.7% / 60.8% by channel.
Is #40bc9b a light or a dark color?
It is a mid-tone. Relative luminance is 0.3942 and perceived brightness is 62%, so black text on it reaches 8.88:1.
Should I use black or white text on #40bc9b?
Black. It scores 8.88:1 against #40bc9b, versus 2.36:1 for white — AAA at any size.
What is the complementary color of #40bc9b?
#BC4061 sits directly opposite on the wheel. Softer options are the split-complements #BC409F and #BC5D40, which give the same contrast with far less vibration.
What colors go well with #40bc9b?
For interface work: #F4FAF9 as the surface, #C2EAE0 for borders, #4B9B85 for secondary text, #C13B80 as an accent and #205F4E for hover and pressed states. For a palette, the analogous pair #40BC5D and #409FBC stays calm, while #BC4061 is the loudest partner.
What is #40bc9b in CMYK for printing?
cmyk(66%, 0%, 18%, 26%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.
Is #40bc9b warm or cool?
Cool — it scores 81 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #40BC6D; nudged cooler, #3DB2BE.