#f51821
a balanced, electric red · warm · closest name: Red
At a glance
Every number on this page in one read: what #f51821 is made of, how bright it looks, and which way it leans.
Reads warm. Warm and cool siblings keep the same lightness, so you can swap one in without redoing your contrast maths.
Every format
| HEX | #f51821 |
| RGB | rgb(245, 24, 33) |
| HSL | hsl(358, 92%, 53%) |
| CMYK | cmyk(0%, 90%, 87%, 4%) |
| LAB | lab(52.0 75.9 54.8) |
| LCH | lch(52.0 93.6 35.8) |
| OKLCH | oklch(0.616 0.243 27.3) |
| Decimal | 16062497 |
| Display P3 | color(display-p3 0.961 0.094 0.129) |
Copy-ready code
/* CSS */
color: #f51821;
background-color: #f51821;
/* Tailwind (arbitrary) */
class="text-[#f51821] bg-[#f51821]"
/* SCSS */
$brand: #f51821;
/* SwiftUI */
Color(red: 0.961, green: 0.094, blue: 0.129)
/* Android */
Color.parseColor("#f51821")
/* Flutter */
Color(0xFFF51821)
/* Python / OpenCV (BGR) */
(33, 24, 245)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. #f51821 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: #FDF2F2;
--brand-100: #FBE4E5;
--brand-200: #F9C3C5;
--brand-300: #FA9398;
--brand-400: #F85E64;
--brand-500: #f51821;
--brand-600: #EB0A13;
--brand-700: #C40810;
--brand-800: #9C070D;
--brand-900: #710A0E;
--brand-950: #470609;
--brand: #f51821;
--brand-ink: #000000;
}Colors that work with #f51821
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 #f51821
Derived from its contrast, chroma and lightness — not from taste.
- ✓Headings from 24px up on white
- ✓Text and icons on dark surfaces
- ✓Primary buttons and calls to action
- ✓Focus rings, active and selected states
- ✓Brand accents, badges and data highlights
- ⚠Small text on white — under 4.5:1
- ⚠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 | #18F5EC | Directly opposite — maximum tension | |
| Analogous left | #F5188F | Neighbour, quieter | |
| Analogous right | #F57E18 | Neighbour, quieter | |
| Split-complement 1 | #18F57E | Contrast without the clash | |
| Split-complement 2 | #188FF5 | Contrast without the clash | |
| Triadic 1 | #21F518 | Even thirds — balanced and loud | |
| Triadic 2 | #1821F5 | Even thirds — balanced and loud | |
| Tetradic | #8FF518 | Fourth corner of the square scheme |
RGB percentages
CMYK percentages
Color previews
#f51821 text on a black background
contrast 5.04:1
#f51821 text on a white background
contrast 4.17:1
CSS3 live lab
The quick brown fox
color: #f51821;
background-color: #f51821;
Glowing headline
text-shadow: 2px 2px 8px #f51821;
Soft neon halo
text-shadow: 0 0 14px rgba(245, 24, 33, 0.45);
box-shadow: 0 12px 32px -8px rgba(245, 24, 33, 0.45);
border: 3px solid #f51821; background: linear-gradient(135deg, #f51821, #F5A218);
Monochromatic scale
Palettes built from #f51821
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: Vermilion (#e34234) — ΔE2000 3.8 away, with its history, psychology and brand usage.
#f51821 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.
#f51821, answered
What color is #f51821?
#f51821 is a balanced electric red, closest to Red (ΔE2000 4.2). It sits at 358° on the hue wheel with 92% saturation and 53% lightness, which reads as warm.
What is the RGB value of #f51821?
rgb(245, 24, 33) — 245 red, 24 green and 33 blue out of 255, or 96.1% / 9.4% / 12.9% by channel.
Is #f51821 a light or a dark color?
It is a mid-tone. Relative luminance is 0.2018 and perceived brightness is 53%, so black text on it reaches 5.04:1.
Should I use black or white text on #f51821?
Black. It scores 5.04:1 against #f51821, versus 4.17:1 for white — AA at any size.
What is the complementary color of #f51821?
#18F5EC sits directly opposite on the wheel. Softer options are the split-complements #18F57E and #188FF5, which give the same contrast with far less vibration.
What colors go well with #f51821?
For interface work: #FAF4F5 as the surface, #EDC0C2 for borders, #9B4B4E for secondary text, #04C88F as an accent and #7A050A for hover and pressed states. For a palette, the analogous pair #F5188F and #F57E18 stays calm, while #18F5EC is the loudest partner.
What is #f51821 in CMYK for printing?
cmyk(0%, 90%, 87%, 4%). 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 #f51821 warm or cool?
Warm — it scores 18 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #F54418; nudged cooler, #F71571.