#3978CE
Closest named color: Windows Blue (#3778BF). oklch(57.5% 0.148 257), rgb(57, 120, 206).
Aa
Black text reads best on this color (4.75:1).
About this color
#3978CE is a medium-dark, vivid blue. In OKLCH its lightness is 57%, its chroma 0.148 and its hue 257°. Its hue sits on the cool side of the wheel. The nearest named color is Windows Blue (#3778BF), ΔE 0.024 away. Black text reads best on it, at 4.75:1.
| Hue family | Blues |
| Lightness | medium-dark (57%) |
| Chroma | vivid (0.148) |
| Temperature | cool |
| Nearest name | Windows Blue (#3778BF) |
| Black text | 4.75:1 |
| White text | 4.41:1 |
Values
| HEX | #3978CE |
| RGB | rgb(57, 120, 206) |
| HSL | hsl(215, 60%, 52%) |
| OKLCH | oklch(57.5% 0.148 257) |
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 #3978CE | 4.41:1 | AA large text | Lc -75.8 | Fine for body text |
| Black text on #3978CE | 4.75:1 | AA | Lc 33.8 | Non-text elements, placeholder text |
| #3978CE text on white | 4.41:1 | AA large text | Lc 70.3 | Content text, not long reading |
| #3978CE text on black | 4.75:1 | AA | Lc -31.4 | 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 600.
-
Step 50
50
#F2F6FC
oklch(97.2% 0.009 258.3)
-
Step 100
100
#E2EBF7
oklch(93.7% 0.019 255.5)
-
Step 200
200
#CADBF2
oklch(88.6% 0.037 256)
-
Step 300
300
#A6C3EC
oklch(81% 0.066 257)
-
Step 400
400
#75A2E2
oklch(70.6% 0.106 257.2)
-
Step 500
500
#508ADA
oklch(63.1% 0.136 256.8)
-
Step 600
600 (this color)
#3978CE
oklch(57.5% 0.148 257)
-
Step 700
700
#265FAD
oklch(49.1% 0.138 257.3)
-
Step 800
800
#214E8C
oklch(42.7% 0.114 257.2)
-
Step 900
900
#204270
oklch(37.8% 0.089 256.6)
-
Step 950
950
#132741
oklch(27% 0.055 255.7)
#3978CE 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) | #4F7FD1 | 0.030 |
| Deuteranopia (no green cones) | #3572CC | 0.017 |
| Tritanopia (no blue cones) | #008C99 | 0.115 |
| Achromatopsia (no color) | #787878 | 0.148 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #3978CE
#3978CE
oklch(57.5% 0.148 257)
- #A06E00
#A06E00
oklch(57.6% 0.12 77.3)
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 #3978CE, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Windows Blue #3778BF ΔE 0.024
- Water Blue #0E87CC ΔE 0.043
- Royal Blue #4169E1 ΔE 0.051
- Nice Blue #107AB0 ΔE 0.055
- Cool Blue #4984B8 ΔE 0.055
- Steel Blue #4682B4 ΔE 0.055
- French Blue #436BAD ΔE 0.057
- Mid Blue #276AB3 ΔE 0.057
Use #3978CE 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.