#51BFEF
Closest named color: Vivid Sky Blue (#4CC9F0). oklch(76.1% 0.121 230.1), rgb(81, 191, 239).
Aa
Black text reads best on this color (10.04:1).
About this color
#51BFEF is a medium-light, moderately saturated blue. In OKLCH its lightness is 76%, its chroma 0.121 and its hue 230°. Its hue sits on the cool side of the wheel. The nearest named color is Vivid Sky Blue (#4CC9F0), ΔE 0.027 away. Black text reads best on it, at 10.04:1.
| Hue family | Blues |
| Lightness | medium-light (76%) |
| Chroma | moderately saturated (0.121) |
| Temperature | cool |
| Nearest name | Vivid Sky Blue (#4CC9F0) |
| Black text | 10.04:1 |
| White text | 2.08:1 |
Values
| HEX | #51BFEF |
| RGB | rgb(81, 191, 239) |
| HSL | hsl(198, 83%, 63%) |
| OKLCH | oklch(76.1% 0.121 230.1) |
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 #51BFEF | 2.08:1 | Fails | Lc -45.2 | Large or bold text, headings |
| Black text on #51BFEF | 10.04:1 | AAA | Lc 63.4 | Content text, not long reading |
| #51BFEF text on white | 2.08:1 | Fails | Lc 40.6 | Non-text elements, placeholder text |
| #51BFEF text on black | 10.04:1 | AAA | Lc -61.7 | Content text, not long reading |
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 300.
-
Step 50
50
#EBF8FE
oklch(97.1% 0.016 227)
-
Step 100
100
#D3EFFD
oklch(93.6% 0.035 229.3)
-
Step 200
200
#ACE2FD
oklch(88.5% 0.067 230.1)
-
Step 300
300 (this color)
#51BFEF
oklch(76.1% 0.121 230.1)
-
Step 400
400
#00AFE7
oklch(70.6% 0.141 230.3)
-
Step 500
500
#0096C7
oklch(63.1% 0.126 230.5)
-
Step 600
600
#007EA7
oklch(55.5% 0.111 230)
-
Step 700
700
#006A8D
oklch(49.1% 0.098 229.8)
-
Step 800
800
#005774
oklch(42.7% 0.085 229.4)
-
Step 900
900
#004862
oklch(37.7% 0.076 230.8)
-
Step 950
950
#002B3C
oklch(27.1% 0.054 230.4)
#51BFEF 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) | #A7BCF1 | 0.084 |
| Deuteranopia (no green cones) | #91ACEE | 0.073 |
| Tritanopia (no blue cones) | #00CCCF | 0.073 |
| Achromatopsia (no color) | #B3B3B3 | 0.121 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #51BFEF
#51BFEF
oklch(76.1% 0.121 230.1)
- #EF9A69
#EF9A69
oklch(76.2% 0.121 50.1)
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 #51BFEF, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Vivid Sky Blue #4CC9F0 ΔE 0.027
- Deep Sky Blue #00BFFF ΔE 0.033
- Bright Sky Blue #02CCFE ΔE 0.039
- Lightblue #7BC8F6 ΔE 0.046
- Sky #82CAFC ΔE 0.057
- Carolina Blue #8AB8FE ΔE 0.060
- Light Sky Blue #87CEFA ΔE 0.067
- Sky Blue #87CEEB ΔE 0.067
Use #51BFEF 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.