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Customizing AstroPaper theme color schemes


This post will explain how you can enable/disable light & dark mode for the website. Moreover, you’ll learn how you can customize color schemes of the entire website.

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Enable/disable light & dark mode

AstroPaper theme will include light and dark mode by default. In other words, there will be two color schemes_ one for light mode and another for dark mode. This default behavior can be disabled in SITE configuration object of the src/config.ts file.

// file: src/config.ts
export const SITE = {
  website: "",
  author: "Sat Naing",
  desc: "A minimal, responsive and SEO-friendly Astro blog theme.",
  title: "AstroPaper",
  ogImage: "astropaper-og.jpg",
  lightAndDarkMode: true, // true by default
  postPerPage: 3,

To disable light & dark mode set SITE.lightAndDarkMode to false.

Choose primary color scheme

By default, if we disable SITE.lightAndDarkMode, we will only get system’s prefers-color-scheme.

Thus, to choose primary color scheme instead of prefers-color-scheme, we have to set color scheme in the primaryColorScheme variable inside public/toggle-theme.js.

/* file: public/toggle-theme.js */
const primaryColorScheme = ""; // "light" | "dark"

// Get theme data from local storage
const currentTheme = localStorage.getItem("theme");

// other codes etc...

The primaryColorScheme variable can hold two values_ "light", "dark". You can leave the empty string (default) if you don’t want to specify the primary color scheme.

  • "" - system’s prefers-color-scheme. (default)
  • "light" - use light mode as primary color scheme.
  • "dark" - use dark mode as primary color scheme.
Why 'primaryColorScheme' is not inside config.ts?

To avoid color flickering on page reload, we have to place the toggle-switch JavaScript codes as early as possible when the page loads. It solves the problem of flickering, but as a trade-off, we cannot use ESM imports anymore.

Click here to know more about Astro’s is:inline script.

Customize color schemes

Both light & dark color schemes of AstroPaper theme can be customized. You can do this in src/styles/base.css file.

/* file: src/styles/base.css */
@tailwind base;
@tailwind components;
@tailwind utilities;

@layer base {
  html[data-theme="light"] {
    --color-fill: 251, 254, 251;
    --color-text-base: 40, 39, 40;
    --color-accent: 0, 108, 172;
    --color-card: 230, 230, 230;
    --color-card-muted: 205, 205, 205;
    --color-border: 236, 233, 233;
  html[data-theme="dark"] {
    --color-fill: 47, 55, 65;
    --color-text-base: 230, 230, 230;
    --color-accent: 26, 217, 217;
    --color-card: 63, 75, 90;
    --color-card-muted: 89, 107, 129;
    --color-border: 59, 70, 85;
  /* other styles */

In AstroPaper theme, :root and html[data-theme="light"] selectors are used as the light color scheme and html[data-theme="dark"] is used the dark color scheme. If you want to customize your custom color scheme, you have to specify your light color scheme inside :root,html[data-theme="light"] and dark color scheme inside html[data-theme="dark"].

Colors are declared in CSS custom property (CSS Variable) notation. Color property values are written in rgb values. (Note: instead of rgb(40, 39, 40), only specify 40, 39, 40)

Here is the detail explanation of color properties.

Color PropertyDefinition & Usage
--color-fillPrimary color of the website. Usually the main background.
--color-text-baseSecondary color of the website. Usually the text color.
--color-accentAccent color of the website. Link color, hover color etc.
--color-cardCard, scrollbar and code background color (like this).
--color-card-mutedCard and scrollbar background color for hover state etc.
--color-borderBorder color. Especially used in horizontal row (hr)

Here is an example of changing the light color scheme.

@layer base {
  /* lobster color scheme */
  html[data-theme="light"] {
    --color-fill: 246, 238, 225;
    --color-text-base: 1, 44, 86;
    --color-accent: 225, 74, 57;
    --color-card: 220, 152, 145;
    --color-card-muted: 233, 119, 106;
    --color-border: 220, 152, 145;

Check out some predefined color schemes AstroPaper has already crafted for you.