Cobalt Blue vs Slate Grey: What's the Difference?

The main difference between Cobalt Blue and Slate Grey is brightness and saturation: both are blue shades, but Slate Grey is lighter and Cobalt Blue is more saturated. Cobalt Blue (#0047AB) has an HSL of 215°, 100%, 34%, whereas Slate Grey (#708090) sits at 210°, 13%, 50%.

Cobalt Blue#0047AB

Slate Grey#708090

#0047ABBlended: #38649E#708090

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Cobalt Blue vs Slate Grey: Key Differences at a Glance

Aspect Cobalt Blue Slate Grey

BrightnessDark (L=34%) — rich, serious, substantialMedium (L=50%) — balanced, versatile

SaturationVivid (S=100%) — bright, energetic, eye-catchingNear-neutral (S=13%) — desaturated and restrained

Hue familyBlueBlue

TemperatureCoolCool

Hex code#0047AB#708090

RGB0, 71, 171112, 128, 144

Can you use Cobalt Blue and Slate Grey together?

Slate Grey text on Cobalt Blue

Cobalt Blue text on Slate Grey

Contrast Ratio:2.08:1Insufficient Contrast

How to Tell Cobalt Blue and Slate Grey Apart

●Look at lightness first: Slate Grey is noticeably lighter.
●Check saturation: Cobalt Blue looks more vivid and saturated.
●Compare them on a white background to see true saturation, and on black to see true lightness.

Cobalt Blue or Slate Grey: Which to Use and Where

Four real design scenarios, with the recommended pick based on hue, saturation, and WCAG contrast.

◆Branding & logos

PickCobalt Blue

Cobalt Blue is more saturated (100% HSL vs 13%) so it reads as bolder and more memorable at logo scale, while Slate Grey can feel washed out when printed small.

▢Web UI & body text backgrounds

PickCobalt Blue

Cobalt Blue hits a 8.44:1 WCAG contrast against white — safer for text-heavy interfaces — where Slate Grey only reaches 4.05:1 and risks failing AA at small body sizes.

⬡Fashion & apparel

PickSlate Grey

Slate Grey is a cool-leaning tone that flatters spring/summer collections and warmer skin undertones, while Cobalt Blue leans cooler and is better suited to autumn/winter layering.

▣Interior design & walls

PickSlate Grey

Slate Grey is the more muted of the two (13% saturation) and sits more calmly on large wall surfaces, while Cobalt Blue's higher chroma can overwhelm a room when used beyond accent pieces.

When to Use Cobalt Blue vs Slate Grey in Design

Use Cobalt Blue for:

●Tech and corporate trust

●Finance and banking brands

●Links and primary buttons

●Medical and professional UI

●Calm dependable visuals

Use Slate Grey for:

●Tech and corporate trust

●Finance and banking brands

●Links and primary buttons

●Medical and professional UI

●Calm dependable visuals

Cobalt Blue and Slate Grey Hex Codes, RGB & HSL

Cobalt Blue#0047AB

Cobalt Blue (#0047AB) is a dark, vivid blue with a cool undertone — it feels rich, serious, substantial and bright, energetic, eye-catching.

HEX

RGB

HSL

HSV

CMYK

PANTONE

Shades

Tints

Slate Grey#708090

Slate Grey (#708090) is a medium, near-neutral blue with a cool undertone — it feels balanced, versatile and desaturated and restrained.

HEX

RGB

HSL

HSV

CMYK

PANTONE

Shades

Tints

Cobalt Blue and Slate Grey WCAG Contrast Ratios

Text legibility depends on the contrast ratio between foreground and background. WCAG 2.1 AA requires at least 4.5:1 for normal text and 3:1 for large text; AAA requires 7:1. Use these numbers to choose accessible combinations for your design.

Sample text preview

Cobalt Blue text on white

8.44:1AAA

Sample text preview

Cobalt Blue text on black

2.49:1Fail

Sample text preview

Slate Grey text on white

4.05:1AA Large

Sample text preview

Slate Grey text on black

5.18:1AA

Sample text preview

Cobalt Blue text on Slate Grey

2.08:1Fail

Sample text preview

Slate Grey text on Cobalt Blue

2.08:1Fail

Explore Cobalt Blue and Slate Grey individually

Each color has a dedicated page with shades, tints, CSS name, pairings, and color psychology.

Cobalt Blue color page#0047AB · shades, tints, pairings Slate Grey color page#708090 · shades, tints, pairings

More Cobalt Blue and Slate Grey Comparisons

Cobalt Blue vs Slate Grey FAQ

What is the difference between cobalt blue and slate grey?+

The main difference between Cobalt Blue and Slate Grey is brightness and saturation: both are blue shades, but Slate Grey is lighter and Cobalt Blue is more saturated. Cobalt Blue (#0047AB) has an HSL of 215°, 100%, 34%, whereas Slate Grey (#708090) sits at 210°, 13%, 50%.

Is cobalt blue darker than slate grey?+

Yes. Cobalt Blue is darker, with a lightness of 34% in HSL compared to Slate Grey at 50% — a 16-point gap.

Are cobalt blue and slate grey the same color?+

No. Cobalt Blue is #0047AB and Slate Grey is #708090. They differ by 5° in hue, 16% in lightness, and 87% in saturation.

Which is more saturated, cobalt blue or slate grey?+

Cobalt Blue is more saturated. In HSL, Cobalt Blue has 100% saturation and Slate Grey has 13% — Cobalt Blue is the more vivid of the two, while Slate Grey reads as more muted.

Is cobalt blue warm or cool?+

Cobalt Blue (#0047AB) is a cool blue. Its hue sits at 215° on the color wheel, which places it in the cool range.

Is slate grey warm or cool?+

Slate Grey (#708090) is a cool blue. Its hue sits at 210° on the color wheel, which places it in the cool range.

Can you use cobalt blue and slate grey together?+

Yes. Both cobalt blue and slate grey are blue shades, so they pair naturally in a monochromatic palette. Use cobalt blue as the dominant color and slate grey as the accent or highlight.

What color family does cobalt blue belong to?+

Cobalt Blue belongs to the blue family. Its HSL is 215°, 100%, 34% — a cool tone within the broader blue group.

What is the hex code for cobalt blue?+

The hex code for Cobalt Blue is #0047AB. In RGB, that's rgb(0, 71, 171), and in HSL it's hsl(215, 100%, 34%).

What is the hex code for slate grey?+

The hex code for Slate Grey is #708090. In RGB, that's rgb(112, 128, 144), and in HSL it's hsl(210, 13%, 50%).