#21B9F8
Closest named color: Deep Sky Blue (#00BFFF). oklch(74% 0.147 233.2), rgb(33, 185, 248).
Aa
Black text reads best on this color (9.35:1).
About this color
#21B9F8 is a medium-light, vivid blue. In OKLCH its lightness is 74%, its chroma 0.147 and its hue 233°. Its hue sits on the cool side of the wheel. The nearest named color is Deep Sky Blue (#00BFFF), ΔE 0.017 away. Black text reads best on it, at 9.35:1.
| Hue family | Blues |
| Lightness | medium-light (74%) |
| Chroma | vivid (0.147) |
| Temperature | cool |
| Nearest name | Deep Sky Blue (#00BFFF) |
| Black text | 9.35:1 |
| White text | 2.24:1 |
Values
| HEX | #21B9F8 |
| RGB | rgb(33, 185, 248) |
| HSL | hsl(198, 94%, 55%) |
| OKLCH | oklch(74% 0.147 233.2) |
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 #21B9F8 | 2.24:1 | Fails | Lc -48.4 | Large or bold text, headings |
| Black text on #21B9F8 | 9.35:1 | AAA | Lc 60.3 | Content text, not long reading |
| #21B9F8 text on white | 2.24:1 | Fails | Lc 43.7 | Non-text elements, placeholder text |
| #21B9F8 text on black | 9.35:1 | AAA | Lc -58.5 | 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
#EEF7FD
oklch(97.1% 0.013 236.6)
-
Step 100
100
#D9EDF9
oklch(93.5% 0.027 234)
-
Step 200
200
#B9E0F6
oklch(88.6% 0.051 232.8)
-
Step 300
300
#82CBF3
oklch(80.9% 0.092 233.5)
-
Step 400
400 (this color)
#21B9F8
oklch(74% 0.147 233.2)
-
Step 500
500
#0095CB
oklch(63% 0.131 233.2)
-
Step 600
600
#007DAB
oklch(55.5% 0.115 233.2)
-
Step 700
700
#006991
oklch(49% 0.102 233.6)
-
Step 800
800
#005677
oklch(42.6% 0.088 233.1)
-
Step 900
900
#004864
oklch(37.8% 0.078 232.8)
-
Step 950
950
#002A3D
oklch(26.9% 0.056 233.8)
#21B9F8 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) | #99B7FB | 0.092 |
| Deuteranopia (no green cones) | #7EA5F7 | 0.077 |
| Tritanopia (no blue cones) | #00CACF | 0.088 |
| Achromatopsia (no color) | #ADADAD | 0.147 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #21B9F8
#21B9F8
oklch(74% 0.147 233.2)
- #F28E49
#F28E49
oklch(74.1% 0.147 52.9)
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 #21B9F8, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Deep Sky Blue #00BFFF ΔE 0.017
- Bright Sky Blue #02CCFE ΔE 0.051
- Vivid Sky Blue #4CC9F0 ΔE 0.055
- Carolina Blue #8AB8FE ΔE 0.076
- Lightblue #7BC8F6 ΔE 0.076
- Turquoise Blue #06B1C4 ΔE 0.077
- Sky #82CAFC ΔE 0.085
- Dark Turquoise #00CED1 ΔE 0.094
Use #21B9F8 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.