#666CC1
Closest named color: Dark Periwinkle (#665FD1). oklch(56.6% 0.13 278.3), rgb(102, 108, 193).
Aa
White text reads best on this color (4.68:1).
About this color
#666CC1 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 57%, its chroma 0.130 and its hue 278°. Its hue sits on the cool side of the wheel. The nearest named color is Dark Periwinkle (#665FD1), ΔE 0.044 away. White text reads best on it, at 4.68:1.
| Hue family | Blues |
| Lightness | medium-dark (57%) |
| Chroma | moderately saturated (0.130) |
| Temperature | cool |
| Nearest name | Dark Periwinkle (#665FD1) |
| Black text | 4.48:1 |
| White text | 4.68:1 |
Values
| HEX | #666CC1 |
| RGB | rgb(102, 108, 193) |
| HSL | hsl(236, 42%, 58%) |
| OKLCH | oklch(56.6% 0.13 278.3) |
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 #666CC1 | 4.68:1 | AA | Lc -77.9 | Fine for body text |
| Black text on #666CC1 | 4.48:1 | AA large text | Lc 31.7 | Non-text elements, placeholder text |
| #666CC1 text on white | 4.68:1 | AA | Lc 72.4 | Content text, not long reading |
| #666CC1 text on black | 4.48:1 | AA large text | Lc -29.3 | 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
#F4F5FB
oklch(97.1% 0.008 278.6)
-
Step 100
100
#E7E9F5
oklch(93.6% 0.016 278.5)
-
Step 200
200
#D4D8EF
oklch(88.6% 0.032 277.9)
-
Step 300
300
#B7BEE7
oklch(81% 0.058 277.4)
-
Step 400
400
#939BDB
oklch(70.8% 0.094 278.2)
-
Step 500
500
#7981D1
oklch(63.1% 0.12 278)
-
Step 600
600 (this color)
#666CC1
oklch(56.6% 0.13 278.3)
-
Step 700
700
#5257A4
oklch(49.1% 0.122 278.1)
-
Step 800
800
#434785
oklch(42.6% 0.102 278.4)
-
Step 900
900
#393C6A
oklch(37.6% 0.078 279.1)
-
Step 950
950
#21243E
oklch(27.1% 0.048 277.6)
#666CC1 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) | #4A77C4 | 0.041 |
| Deuteranopia (no green cones) | #4370BF | 0.043 |
| Tritanopia (no blue cones) | #457E8D | 0.114 |
| Achromatopsia (no color) | #747474 | 0.130 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666CC1
#666CC1
oklch(56.6% 0.13 278.3)
- #887600
#887600
oklch(56.5% 0.117 98.6)
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 #666CC1, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dark Periwinkle #665FD1 ΔE 0.044
- Slate Blue #6A5ACD ΔE 0.051
- Light Indigo #6D5ACF ΔE 0.052
- Iris #6258C4 ΔE 0.053
- French Blue #436BAD ΔE 0.055
- Windows Blue #3778BF ΔE 0.057
- Royal Blue #4169E1 ΔE 0.067
- Deep Lavender #8D5EB7 ΔE 0.067
Use #666CC1 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.