#21B4EF
Closest named color: Deep Sky Blue (#00BFFF). oklch(72.5% 0.141 232.2), rgb(33, 180, 239).
Aa
Black text reads best on this color (8.83:1).
About this color
#21B4EF is a medium-light, vivid blue. In OKLCH its lightness is 72%, its chroma 0.141 and its hue 232°. Its hue sits on the cool side of the wheel. The nearest named color is Deep Sky Blue (#00BFFF), ΔE 0.033 away. Black text reads best on it, at 8.83:1.
| Hue family | Blues |
| Lightness | medium-light (72%) |
| Chroma | vivid (0.141) |
| Temperature | cool |
| Nearest name | Deep Sky Blue (#00BFFF) |
| Black text | 8.83:1 |
| White text | 2.37:1 |
Values
| HEX | #21B4EF |
| RGB | rgb(33, 180, 239) |
| HSL | hsl(197, 87%, 53%) |
| OKLCH | oklch(72.5% 0.141 232.2) |
Contrast
WCAG 2 contrast ratios are the conformance target: AA needs 4.5:1 for body text and 3:1 for large text, AAA needs 7:1. APCA Lc values are supplementary guidance from the WCAG 3 drafts.
| Pair | WCAG 2 | Result | APCA | APCA guidance |
|---|---|---|---|---|
| White text on #21B4EF | 2.37:1 | Fails | Lc -51.2 | Large or bold text, headings |
| Black text on #21B4EF | 8.83:1 | AAA | Lc 57.7 | Large or bold text, headings |
| #21B4EF text on white | 2.37:1 | Fails | Lc 46.3 | Large or bold text, headings |
| #21B4EF text on black | 8.83:1 | AAA | Lc -55.8 | Large or bold text, headings |
Tints and shades
A 50–950 scale built in OKLCH: the hue is held, lightness follows a Tailwind v4-like curve, and every step is kept inside the sRGB gamut. This color sits at step 400.
-
Step 50
50
#EEF7FC
oklch(97.1% 0.012 231.7)
-
Step 100
100
#DAEDF8
oklch(93.5% 0.025 233)
-
Step 200
200
#BAE0F4
oklch(88.6% 0.048 230.9)
-
Step 300
300
#84CBF0
oklch(80.9% 0.088 232.1)
-
Step 400
400 (this color)
#21B4EF
oklch(72.5% 0.141 232.2)
-
Step 500
500
#0096CA
oklch(63.2% 0.129 232.1)
-
Step 600
600
#007EAA
oklch(55.7% 0.113 231.8)
-
Step 700
700
#006A90
oklch(49.2% 0.1 232)
-
Step 800
800
#005676
oklch(42.6% 0.087 232.3)
-
Step 900
900
#004863
oklch(37.7% 0.077 231.8)
-
Step 950
950
#002B3D
oklch(27.1% 0.055 231.9)
#21B4EF with color blindness
Simulated with the Machado et al. (2009) model. ΔE is how far the color moves: below about 0.02 you would not notice a change.
| Vision | Seen as | Shift (ΔE) |
|---|---|---|
| Protanopia (no red cones) | #96B2F2 | 0.091 |
| Deuteranopia (no green cones) | #7CA0EE | 0.077 |
| Tritanopia (no blue cones) | #00C4C8 | 0.084 |
| Achromatopsia (no color) | #A8A8A8 | 0.142 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #21B4EF
#21B4EF
oklch(72.5% 0.141 232.2)
- #EA8A4A
#EA8A4A
oklch(72.4% 0.141 52.3)
Analogous
Neighbouring hues, 30° either side.
Split complementary
The two hues beside the complement (150° and 210°).
Triadic
Three hues spaced 120° apart.
Palettes with this color
Curated palettes that contain a color within ΔE 0.04 (OKLab) of #21B4EF, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Deep Sky Blue #00BFFF ΔE 0.033
- Bright Sky Blue #02CCFE ΔE 0.064
- Turquoise Blue #06B1C4 ΔE 0.065
- Vivid Sky Blue #4CC9F0 ΔE 0.065
- Carolina Blue #8AB8FE ΔE 0.083
- Chefchaouen Blue #4895EF ΔE 0.084
- Lightblue #7BC8F6 ΔE 0.086
- Cornflower Blue #6495ED ΔE 0.087
Use #21B4EF in your product
Turn it into light and dark UI roles checked for contrast, then export to Tailwind v4, shadcn/ui, CSS or design tokens.