#166FDB
Closest named color: Cerulean Blue (#056EEE). oklch(55.5% 0.183 256.9), rgb(22, 111, 219).
Aa
White text reads best on this color (4.84:1).
About this color
#166FDB is a medium-dark, vivid blue. In OKLCH its lightness is 56%, its chroma 0.183 and its hue 257°. Its hue sits on the cool side of the wheel. The nearest named color is Cerulean Blue (#056EEE), ΔE 0.029 away. White text reads best on it, at 4.84:1.
| Hue family | Blues |
| Lightness | medium-dark (56%) |
| Chroma | vivid (0.183) |
| Temperature | cool |
| Nearest name | Cerulean Blue (#056EEE) |
| Black text | 4.33:1 |
| White text | 4.84:1 |
Values
| HEX | #166FDB |
| RGB | rgb(22, 111, 219) |
| HSL | hsl(213, 82%, 47%) |
| OKLCH | oklch(55.5% 0.183 256.9) |
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 #166FDB | 4.84:1 | AA | Lc -78.4 | Fine for body text |
| Black text on #166FDB | 4.33:1 | AA large text | Lc 31.1 | Non-text elements, placeholder text |
| #166FDB text on white | 4.84:1 | AA | Lc 73.0 | Content text, not long reading |
| #166FDB text on black | 4.33:1 | AA large text | Lc -28.7 | Dividers and decoration only |
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 600.
-
Step 50
50
#F1F6FD
oklch(97.1% 0.011 256.7)
-
Step 100
100
#E0EBFA
oklch(93.6% 0.024 256.1)
-
Step 200
200
#C6DBF8
oklch(88.5% 0.046 256.5)
-
Step 300
300
#9FC3F6
oklch(80.9% 0.082 257.1)
-
Step 400
400
#69A2F2
oklch(70.7% 0.132 257)
-
Step 500
500
#3D88ED
oklch(63.1% 0.169 256.9)
-
Step 600
600 (this color)
#166FDB
oklch(55.5% 0.183 256.9)
-
Step 700
700
#055CBE
oklch(49% 0.17 257)
-
Step 800
800
#0C4C9A
oklch(42.7% 0.141 256.9)
-
Step 900
900
#14407A
oklch(37.6% 0.11 256.9)
-
Step 950
950
#0D2648
oklch(27% 0.07 257)
#166FDB 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) | #2A7ADF | 0.033 |
| Deuteranopia (no green cones) | #006AD9 | 0.016 |
| Tritanopia (no blue cones) | #00899A | 0.138 |
| Achromatopsia (no color) | #717171 | 0.183 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #166FDB
#166FDB
oklch(55.5% 0.183 256.9)
- #996800
#996800
oklch(55.5% 0.116 76.4)
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 #166FDB, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Cerulean Blue #056EEE ΔE 0.029
- Royal Blue #4169E1 ΔE 0.032
- Azul #1D5DEC ΔE 0.051
- Neon Blue #4361EE ΔE 0.052
- Windows Blue #3778BF ΔE 0.057
- Bright Blue #0165FC ΔE 0.057
- Clear Blue #247AFD ΔE 0.058
- Mid Blue #276AB3 ΔE 0.062
Use #166FDB 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.