---
name: Hex color
slug: hex-color
category: color
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: A colour written as a hash followed by three, four, six or eight
  hexadecimal digits, the notation most handoffs still speak even when the
  source is OKLCH.
aliases:
  - name: hex code
    source: community
  - name: hex value
    source: community
  - name: "#RRGGBB"
  - name: 8-digit hex
    source: community
tags:
  - web-platform
relations:
  contrastWith:
    - named-color
    - srgb
    - oklch
  variantOf: []
  partOf: []
  seeAlso: []
implementations: []
sources:
  - title: "MDN: <color> CSS type"
    url: https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Values/color_value
demo: inline
exhibit: false
useWhen: the notation a colour is handed over in
---

A hex colour is three numbers in a trench coat. The six digit form is three pairs, red
then green then blue, each pair a byte written in base 16 and therefore running from
`00` to `FF`, which is 0 to 255. `#4F46E5` is red 79, green 70, blue 229. Nothing about
the notation is a colour model of its own: it is sRGB, the same coordinates
`rgb(79 70 229)` names, in a spelling that fits in one token and survives being pasted
into a chat window.

The short forms are the ones that trip people. Three digits expand by doubling each
digit, so `#f0c` is `#ff00cc` and not `#f00c00`, which is why only a lucky subset of
colours can be written short. Four and eight digit forms append alpha in the same way:
`#4F46E5CC` is that indigo at 80 percent opacity, and `#f0c8` is `#ff00cc88`. Case does
not matter to a parser, though a codebase that mixes `#FFF` and `#fff` will fail its own
diff review eventually. Alpha in the value is worth watching, because a colour carrying
its own transparency is a different thing to reason about than a solid one sitting under
an [opacity](/opacity) property.

What hex is bad at is arithmetic. Reading `#4F46E5` tells you almost nothing about how
light the colour is, and there is no digit you can nudge to make it a step darker without
also swinging the hue. That is the whole argument for authoring in
[OKLCH](/oklch) and for building a [colour ramp](/color-ramp) in a space where the
numbers mean something, then letting the build step emit hex for the places that still
need it. Hex is also capped at sRGB: a colour outside that gamut has no hex spelling at
all, so a notation that once described every colour a screen could show now describes
only the older ones.

The staying power is social rather than technical. Hex is what a design tool puts on the
clipboard, what a brand guideline prints, and what someone reads out loud in a meeting,
so it remains the handoff format even for teams whose tokens are authored somewhere
else. Treat it as an output format, not as the place decisions get made.