Night Owl

#5d7b89

A cyan that is nearly neutral — the hue shows only against a true grey. It is mid — the hardest range to put text on, either colour struggles.

Hex

#5d7b89

RGB

93, 123, 137

OKLCh

56.5% 0.041 228.2°

CIELAB (D50)

49.7, -8.5, -11.3

What is true of this colour, and of no other

6 other named colours sit within ΔE00 2 of it.
It uses only 37% of the chroma available at this lightness and hue — there is a far more vivid version of this colour inside sRGB.
As text on white it measures APCA Lc 71.3; on black, Lc -30.4. The sign is the polarity, which the WCAG ratio discards.
Built into an eleven-step scale, 10 of the 10 adjacent pairs stay ΔE00 2 apart — see the ramp.
protanopia and deuteranopia and tritanopia shift it by ΔE00 13.2 and 14.1 and 13.9 — no red cone.

Text on this colour

White text

4.51:1 — passes AA

Black text

4.66:1 — passes AA

Black text is the better of the two at4.66:1. That is enough for body text.

The same colour, with one cone missing

As you see it

#5d7b89

protanopia

#787889 · ΔE00 13.2

deuteranopia

#737389 · ΔE00 14.1

tritanopia

#6d6dbe · ΔE00 13.9

Run a whole palette through all three

The twelve nearest named colours

Ranked by CIEDE2000 — perceptual distance, not hex arithmetic. The closest isOcean Shadow at ΔE00 1.157: between 1 and 2 — a trained eye spots it when the two touch; nobody spots it across a room. What the numbers mean.

Ocean ShadowΔE00 1.157 · #5b7886
ProvidenceΔE00 1.202 · #5c7b8c
Country LakeΔE00 1.32 · #5d7a85
Catalina CoastΔE00 1.385 · #5c7884
Technical BlueΔE00 1.609 · #587c8d
Rocky HillΔE00 1.846 · #567b8a
PassagewayΔE00 2.149 · #647b86
Whale SharkΔE00 2.154 · #607c8e
Hampton SurfΔE00 2.341 · #597681
Windy SeasΔE00 2.379 · #667f8b
Tool BlueΔE00 2.391 · #637985
HokiΔE00 2.43 · #647d86

11 of these have no page of their own: pages exist for the 4,961 colours the dataset marks as good names.