#28378A
Closest named color: Cobalt (#1E488F). oklch(37.8% 0.139 270.5), rgb(40, 55, 138).
Aa
White text reads best on this color (10.48:1).
About this color
#28378A is a dark, moderately saturated blue. In OKLCH its lightness is 38%, its chroma 0.139 and its hue 271°. Its hue sits on the cool side of the wheel. The nearest named color is Cobalt (#1E488F), ΔE 0.045 away. White text reads best on it, at 10.48:1.
| Hue family | Blues |
| Lightness | dark (38%) |
| Chroma | moderately saturated (0.139) |
| Temperature | cool |
| Nearest name | Cobalt (#1E488F) |
| Black text | 2.00:1 |
| White text | 10.48:1 |
Values
| HEX | #28378A |
| RGB | rgb(40, 55, 138) |
| HSL | hsl(231, 55%, 35%) |
| OKLCH | oklch(37.8% 0.139 270.5) |
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 #28378A | 10.48:1 | AAA | Lc -97.9 | Preferred for body text |
| Black text on #28378A | 2.00:1 | Fails | Lc 10.0 | Not readable |
| #28378A text on white | 10.48:1 | AAA | Lc 93.9 | Preferred for body text |
| #28378A text on black | 2.00:1 | Fails | Lc -8.7 | Not readable |
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 900.
-
Step 50
50
#F2F5FF
oklch(97.1% 0.014 272.7)
-
Step 100
100
#E2E9FF
oklch(93.5% 0.031 271.7)
-
Step 200
200
#CBD8FF
oklch(88.5% 0.056 270.7)
-
Step 300
300
#A9BEFF
oklch(80.9% 0.095 270.4)
-
Step 400
400
#7D99FF
oklch(70.7% 0.152 270.5)
-
Step 500
500
#5E7BFF
oklch(63.1% 0.198 270.4)
-
Step 600
600
#465CF7
oklch(55.6% 0.23 270.6)
-
Step 700
700
#384AD8
oklch(49.1% 0.215 270.4)
-
Step 800
800
#2E3EAE
oklch(42.7% 0.178 270.5)
-
Step 900
900 (this color)
#28378A
oklch(37.8% 0.139 270.5)
-
Step 950
950
#172151
oklch(27% 0.089 270.5)
#28378A 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) | #00448D | 0.039 |
| Deuteranopia (no green cones) | #003B88 | 0.030 |
| Tritanopia (no blue cones) | #004C5B | 0.113 |
| Achromatopsia (no color) | #3F3F3F | 0.139 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #28378A
#28378A
oklch(37.8% 0.139 270.5)
- #513F00
#513F00
oklch(37.6% 0.077 90.4)
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 #28378A, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Cobalt #1E488F ΔE 0.045
- Twilight Blue #0A437A ΔE 0.049
- Dark Slate Blue #483D8B ΔE 0.053
- Sapphire #2138AB ΔE 0.055
- Blueberry #464196 ΔE 0.057
- Marine Blue #01386A ΔE 0.065
- Light Navy #155084 ΔE 0.071
- Dusk Blue #26538D ΔE 0.077
Use #28378A 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.