#666CDB
Closest named color: Dark Periwinkle (#665FD1). oklch(58.3% 0.166 277.6), rgb(102, 108, 219).
Aa
Black text reads best on this color (4.73:1).
About this color
#666CDB is a medium-dark, vivid blue. In OKLCH its lightness is 58%, its chroma 0.166 and its hue 278°. Its hue sits on the cool side of the wheel. The nearest named color is Dark Periwinkle (#665FD1), ΔE 0.034 away. Black text reads best on it, at 4.73:1.
| Hue family | Blues |
| Lightness | medium-dark (58%) |
| Chroma | vivid (0.166) |
| Temperature | cool |
| Nearest name | Dark Periwinkle (#665FD1) |
| Black text | 4.73:1 |
| White text | 4.43:1 |
Values
| HEX | #666CDB |
| RGB | rgb(102, 108, 219) |
| HSL | hsl(237, 62%, 63%) |
| OKLCH | oklch(58.3% 0.166 277.6) |
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 #666CDB | 4.43:1 | AA large text | Lc -76.0 | Fine for body text |
| Black text on #666CDB | 4.73:1 | AA | Lc 33.6 | Non-text elements, placeholder text |
| #666CDB text on white | 4.43:1 | AA large text | Lc 70.5 | Content text, not long reading |
| #666CDB text on black | 4.73:1 | AA | Lc -31.1 | Non-text elements, placeholder text |
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
#F4F5FC
oklch(97.1% 0.009 279.7)
-
Step 100
100
#E6E9F9
oklch(93.6% 0.022 277.5)
-
Step 200
200
#D2D7F5
oklch(88.5% 0.042 278)
-
Step 300
300
#B4BDF1
oklch(80.9% 0.074 277)
-
Step 400
400
#8F99EA
oklch(70.8% 0.119 277.5)
-
Step 500
500
#757DE4
oklch(63.1% 0.153 277.7)
-
Step 600
600 (this color)
#666CDB
oklch(58.3% 0.166 277.6)
-
Step 700
700
#4F52B6
oklch(49.1% 0.155 277.8)
-
Step 800
800
#404493
oklch(42.7% 0.128 277.4)
-
Step 900
900
#363A75
oklch(37.7% 0.099 277.6)
-
Step 950
950
#1F2245
oklch(26.9% 0.064 277.4)
#666CDB 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) | #337DDF | 0.061 |
| Deuteranopia (no green cones) | #2273D9 | 0.065 |
| Tritanopia (no blue cones) | #2F8599 | 0.146 |
| Achromatopsia (no color) | #787878 | 0.167 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666CDB
#666CDB
oklch(58.3% 0.166 277.6)
- #8F7B00
#8F7B00
oklch(58.4% 0.121 97.7)
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 #666CDB, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dark Periwinkle #665FD1 ΔE 0.034
- Medium Slate Blue #7B68EE ΔE 0.043
- Light Indigo #6D5ACF ΔE 0.045
- Slate Blue #6A5ACD ΔE 0.046
- Royal Blue #4169E1 ΔE 0.047
- Cornflower #6A79F7 ΔE 0.051
- Iris #6258C4 ΔE 0.058
- Neon Blue #4361EE ΔE 0.061
Use #666CDB 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.