#666AF3
Closest named color: Medium Slate Blue (#7B68EE). oklch(59.6% 0.201 277.1), rgb(102, 106, 243).
Aa
Black text reads best on this color (4.92:1).
About this color
#666AF3 is a medium-dark, vivid blue. In OKLCH its lightness is 60%, its chroma 0.201 and its hue 277°. Its hue sits on the cool side of the wheel. The nearest named color is Medium Slate Blue (#7B68EE), ΔE 0.031 away. Black text reads best on it, at 4.92:1.
| Hue family | Blues |
| Lightness | medium-dark (60%) |
| Chroma | vivid (0.201) |
| Temperature | cool |
| Nearest name | Medium Slate Blue (#7B68EE) |
| Black text | 4.92:1 |
| White text | 4.26:1 |
Values
| HEX | #666AF3 |
| RGB | rgb(102, 106, 243) |
| HSL | hsl(238, 85%, 68%) |
| OKLCH | oklch(59.6% 0.201 277.1) |
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 #666AF3 | 4.26:1 | AA large text | Lc -74.6 | Content text, not long reading |
| Black text on #666AF3 | 4.92:1 | AA | Lc 35.0 | Non-text elements, placeholder text |
| #666AF3 text on white | 4.26:1 | AA large text | Lc 69.1 | Content text, not long reading |
| #666AF3 text on black | 4.92:1 | AA | Lc -32.6 | 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 500.
-
Step 50
50
#F3F5FF
oklch(97.2% 0.013 277.1)
-
Step 100
100
#E5E9FD
oklch(93.7% 0.027 276.8)
-
Step 200
200
#CFD7FE
oklch(88.6% 0.054 276.1)
-
Step 300
300
#B1BBFF
oklch(80.9% 0.097 277.5)
-
Step 400
400
#8A95FF
oklch(70.7% 0.154 277.2)
-
Step 500
500 (this color)
#666AF3
oklch(59.6% 0.201 277.1)
-
Step 600
600
#5B59EF
oklch(55.7% 0.219 277.2)
-
Step 700
700
#4B47D0
oklch(49% 0.204 277.1)
-
Step 800
800
#3D3CA8
oklch(42.7% 0.168 277)
-
Step 900
900
#333585
oklch(37.7% 0.131 277)
-
Step 950
950
#1E204E
oklch(27.1% 0.083 277.4)
#666AF3 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) | #0080F8 | 0.078 |
| Deuteranopia (no green cones) | #0075F0 | 0.073 |
| Tritanopia (no blue cones) | #008AA4 | 0.174 |
| Achromatopsia (no color) | #7A7A7A | 0.202 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666AF3
#666AF3
oklch(59.6% 0.201 277.1)
- #947E00
#947E00
oklch(59.6% 0.123 96.8)
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 #666AF3, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Medium Slate Blue #7B68EE ΔE 0.031
- Cornflower #6A79F7 ΔE 0.037
- Neon Blue #4361EE ΔE 0.051
- Royal Blue #4169E1 ΔE 0.053
- Dark Periwinkle #665FD1 ΔE 0.056
- Light Indigo #6D5ACF ΔE 0.064
- Clear Blue #247AFD ΔE 0.065
- Purpley #8756E4 ΔE 0.066
Use #666AF3 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.