Slack Text Color: You Cannot Color Text, but 3 Things Show Color

You cannot change the color of text in Slack. The message box has no color button, no Markdown or Slack syntax sets a color, canvases have no text color menu, and the API refuses a color style. Three things do put color in a message: a hex code like #22c55e gets a small color square next to it, inline code shows in red, and messages sent by an app can carry a colored bar on the left.

We tried each route on 29 September 2026 in Slack in the browser, in a one-person test workspace, by typing in the message box and by sending messages through chat.postMessage. Everything below is from those runs.

Every route we tried

The API refuses a color style

Slack's rich_text blocks let each piece of text carry a style: bold, italic, strike and code. We added a color to the style and sent it with chat.postMessage:

{
  "type": "text",
  "text": "red text",
  "style": { "color": "#ff0000" }
}

The response:

{
  "ok": false,
  "error": "invalid_blocks",
  "errors": [
    "invalid additional property: color [json-pointer:/blocks/0/elements/0/elements/0/style]"
  ]
}

So apps cannot send colored words either.

Hex codes get a color swatch

When a message contains a hex color code, Slack draws a square in that color right after it. We typed "#ef4444 and #3b82f6" in the message box. Slack changed both to capitals and showed a red and a blue square. Reading the message back with conversations.history shows why: Slack stored each code as its own color element, not as text:

{"type": "color", "value": "#EF4444"}

A plain chat.postMessage with "#22c55e" in the text got the same element and the same green square. Apps can also send {"type": "color", "value": "#22c55e"} inside a rich_text block, and Slack accepted it. Designers use this to share a palette: the code stays copyable and the square shows the color. It does not color the words around it.

Inline code shows in red

Text between backticks is the only way to get colored words in a normal message, and the color is fixed. In Slack's light theme we read the computed style of an inline code element: text rgb(192, 19, 67), which is #C01343, a dark red, on a light gray background, in the Slack-Roboto-Mono font. You cannot choose another color, and a reader may take red code for an error. More about backticks and code blocks is in how to bold text in Slack.

Apps can add a colored bar

Messages sent through the API can include legacy attachments, and each attachment takes a color. This is the part of our test message that drew the green and red bars in the screenshot above:

"attachments": [
  {"color": "#22c55e", "text": "Deploy finished: all checks passed"},
  {"color": "#ef4444", "text": "Deploy failed: 2 tests red"}
]

The text stays black. Only the bar takes the color. Build and alert bots use this for pass and fail. You need an app or a token to send it, and Slack calls attachments a legacy feature, though it still rendered them in our test. The Slack message formatter shows what the formatting marks do before you send.