#666DF0
Closest named color: Medium Slate Blue (#7B68EE). oklch(59.9% 0.193 276.5), rgb(102, 109, 240).
Aa
Black text reads best on this color (5.01:1).
About this color
#666DF0 is a medium-dark, vivid blue. In OKLCH its lightness is 60%, its chroma 0.193 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 5.01:1.
| Hue family | Blues |
| Lightness | medium-dark (60%) |
| Chroma | vivid (0.193) |
| Temperature | cool |
| Nearest name | Medium Slate Blue (#7B68EE) |
| Black text | 5.01:1 |
| White text | 4.19:1 |
Values
| HEX | #666DF0 |
| RGB | rgb(102, 109, 240) |
| HSL | hsl(237, 82%, 67%) |
| OKLCH | oklch(59.9% 0.193 276.5) |
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 #666DF0 | 4.19:1 | AA large text | Lc -74.0 | Content text, not long reading |
| Black text on #666DF0 | 5.01:1 | AA | Lc 35.5 | Non-text elements, placeholder text |
| #666DF0 text on white | 4.19:1 | AA large text | Lc 68.5 | Content text, not long reading |
| #666DF0 text on black | 5.01:1 | AA | Lc -33.1 | 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 500.
-
Step 50
50
#F3F5FE
oklch(97.1% 0.012 276.1)
-
Step 100
100
#E5E9FD
oklch(93.7% 0.027 276.8)
-
Step 200
200
#CFD7FD
oklch(88.5% 0.053 275.9)
-
Step 300
300
#B0BCFE
oklch(81% 0.094 276.1)
-
Step 400
400
#8996FD
oklch(70.8% 0.15 276.4)
-
Step 500
500 (this color)
#666DF0
oklch(59.9% 0.193 276.5)
-
Step 600
600
#5A5BEA
oklch(55.5% 0.21 276.8)
-
Step 700
700
#4A4ACC
oklch(49.1% 0.196 276.4)
-
Step 800
800
#3C3EA5
oklch(42.7% 0.162 276.2)
-
Step 900
900
#333683
oklch(37.7% 0.127 276.8)
-
Step 950
950
#1D204C
oklch(26.8% 0.08 276.6)
#666DF0 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) | #0982F4 | 0.076 |
| Deuteranopia (no green cones) | #0076ED | 0.072 |
| Tritanopia (no blue cones) | #008CA4 | 0.170 |
| Achromatopsia (no color) | #7C7C7C | 0.194 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666DF0
#666DF0
oklch(59.9% 0.193 276.5)
- #957F00
#957F00
oklch(59.9% 0.123 96.9)
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 #666DF0, closest first.
No curated palette has a color within ΔE 0.04 of #666DF0.
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 0.031
- Royal Blue #4169E1 ΔE 0.052
- Neon Blue #4361EE ΔE 0.055
- Dark Periwinkle #665FD1 ΔE 0.055
- Clear Blue #247AFD ΔE 0.063
- Light Indigo #6D5ACF ΔE 0.064
- Slate Blue #6A5ACD ΔE 0.066
Use #666DF0 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.