#666C99
Closest named color: Dull Blue (#49759C). oklch(54.4% 0.071 277.9), rgb(102, 108, 153).
Aa
White text reads best on this color (5.03:1).
About this color
#666C99 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 54%, its chroma 0.071 and its hue 278°. Its hue sits on the cool side of the wheel. The nearest named color is Dull Blue (#49759C), ΔE 0.041 away. White text reads best on it, at 5.03:1.
| Hue family | Blues |
| Lightness | medium-dark (54%) |
| Chroma | moderately saturated (0.071) |
| Temperature | cool |
| Nearest name | Dull Blue (#49759C) |
| Black text | 4.16:1 |
| White text | 5.03:1 |
Values
| HEX | #666C99 |
| RGB | rgb(102, 108, 153) |
| HSL | hsl(233, 20%, 50%) |
| OKLCH | oklch(54.4% 0.071 277.9) |
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 #666C99 | 5.03:1 | AA | Lc -80.2 | Fine for body text |
| Black text on #666C99 | 4.16:1 | AA large text | Lc 29.3 | Dividers and decoration only |
| #666C99 text on white | 5.03:1 | AA | Lc 74.8 | Content text, not long reading |
| #666C99 text on black | 4.16:1 | AA large text | Lc -26.9 | 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
#F5F5F8
oklch(97.1% 0.004 286.3)
-
Step 100
100
#E8E9F0
oklch(93.5% 0.009 279.7)
-
Step 200
200
#D6D8E5
oklch(88.5% 0.018 279)
-
Step 300
300
#BBBFD6
oklch(80.9% 0.033 277.8)
-
Step 400
400
#999EC1
oklch(70.7% 0.051 278.6)
-
Step 500
500
#8086B1
oklch(63.1% 0.065 278.2)
-
Step 600
600 (this color)
#666C99
oklch(54.4% 0.071 277.9)
-
Step 700
700
#585D86
oklch(49.1% 0.066 278.3)
-
Step 800
800
#484C6D
oklch(42.7% 0.055 278.5)
-
Step 900
900
#3C4058
oklch(37.8% 0.041 276.9)
-
Step 950
950
#232534
oklch(26.9% 0.028 278.4)
#666C99 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) | #5E719B | 0.016 |
| Deuteranopia (no green cones) | #5B6D98 | 0.015 |
| Tritanopia (no blue cones) | #58747C | 0.062 |
| Achromatopsia (no color) | #6F6F6F | 0.071 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666C99
#666C99
oklch(54.4% 0.071 277.9)
- #7B703E
#7B703E
oklch(54.4% 0.071 97.3)
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 #666C99, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dull Blue #49759C ΔE 0.041
- Metallic Blue #4F738E ΔE 0.042
- Stormy Blue #507B9C ΔE 0.047
- Grey Purple #826D8C ΔE 0.048
- Dark Lavender #856798 ΔE 0.049
- Muted Blue #3B719F ΔE 0.051
- Flat Blue #3C73A8 ΔE 0.052
- French Blue #436BAD ΔE 0.053
Use #666C99 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.