#666EE7
Closest named color: Medium Slate Blue (#7B68EE). oklch(59.5% 0.18 276.6), rgb(102, 110, 231).
Aa
Black text reads best on this color (4.94:1).
About this color
#666EE7 is a medium-dark, vivid blue. In OKLCH its lightness is 59%, its chroma 0.180 and its hue 277°. Its hue sits on the cool side of the wheel. The nearest named color is Medium Slate Blue (#7B68EE), ΔE 0.034 away. Black text reads best on it, at 4.94:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | vivid (0.180) |
| Temperature | cool |
| Nearest name | Medium Slate Blue (#7B68EE) |
| Black text | 4.94:1 |
| White text | 4.24:1 |
Values
| HEX | #666EE7 |
| RGB | rgb(102, 110, 231) |
| HSL | hsl(236, 73%, 65%) |
| OKLCH | oklch(59.5% 0.18 276.6) |
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 #666EE7 | 4.24:1 | AA large text | Lc -74.5 | Content text, not long reading |
| Black text on #666EE7 | 4.94:1 | AA | Lc 35.1 | Non-text elements, placeholder text |
| #666EE7 text on white | 4.24:1 | AA large text | Lc 69.0 | Content text, not long reading |
| #666EE7 text on black | 4.94:1 | AA | Lc -32.7 | 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
#E5E9FB
oklch(93.6% 0.025 275.9)
-
Step 200
200
#D0D7FA
oklch(88.5% 0.049 276.4)
-
Step 300
300
#B1BCFA
oklch(80.9% 0.089 276.4)
-
Step 400
400
#8A97F7
oklch(70.7% 0.141 276.3)
-
Step 500
500 (this color)
#666EE7
oklch(59.5% 0.18 276.6)
-
Step 600
600
#5B5FE2
oklch(55.6% 0.195 276.7)
-
Step 700
700
#4B4DC5
oklch(49.1% 0.183 276.6)
-
Step 800
800
#3D409F
oklch(42.7% 0.151 276.5)
-
Step 900
900
#33387E
oklch(37.7% 0.117 276.2)
-
Step 950
950
#1E214A
oklch(27% 0.075 277)
#666EE7 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) | #2780EB | 0.066 |
| Deuteranopia (no green cones) | #0376E4 | 0.072 |
| Tritanopia (no blue cones) | #1D8AA0 | 0.158 |
| Achromatopsia (no color) | #7B7B7B | 0.181 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666EE7
#666EE7
oklch(59.5% 0.18 276.6)
- #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 #666EE7, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Medium Slate Blue #7B68EE ΔE 0.034
- Cornflower #6A79F7 ΔE 0.035
- Dark Periwinkle #665FD1 ΔE 0.047
- Royal Blue #4169E1 ΔE 0.048
- Light Indigo #6D5ACF ΔE 0.057
- Neon Blue #4361EE ΔE 0.058
- Slate Blue #6A5ACD ΔE 0.059
- Soft Blue #6488EA ΔE 0.065
Use #666EE7 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.