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Theming

Theming

Using CSS Variables or Tailwind CSS for theming.

We use CSS variables for styling. This allows you to easily change the colors of components without having to update class names.

CSS variables must be defined without the color space function. See the Tailwind CSS documentation for more information.

Convention

We use a simple background and foreground convention for colors. The background variable is used for the background color of the component and the foreground variable is used for the text color.

The background suffix can be omitted if the variable is used for the background color of the component.

Given the following CSS variables:

--primary: 222.2 47.4% 11.2%;
--primary-foreground: 210 40% 98%;

The background color of the following component will be hsl(var(--primary)) and the foreground color will be hsl(var(--primary-foreground)).

div {
    className = ClassName("bg-primary text-primary-foreground")
    + "Hello"
}

CSS Variables

Here's the list of variables available for customization:

Default background color of <body />...etc 
--background: 0 0% 100%;
--foreground: 222.2 47.4% 11.2%;
Muted backgrounds such as <TabsList />, <Skeleton /> and <Switch /> 
--muted: 210 40% 96.1%;
--muted-foreground: 215.4 16.3% 46.9%;
Background color for <Card /> 
--card: 0 0% 100%;
--card-foreground: 222.2 47.4% 11.2%;
Background color for popovers such as <DropdownMenu />, <HoverCard />, <Popover /> 
--popover: 0 0% 100%;
--popover-foreground: 222.2 47.4% 11.2%;
Default border color 
--border: 214.3 31.8% 91.4%;
Border color for inputs such as <Input />, <Select />, <Textarea /> 
--input: 214.3 31.8% 91.4%;
Primary colors for <Button /> 
--primary: 222.2 47.4% 11.2%;
--primary-foreground: 210 40% 98%;
Secondary colors for <Button /> 
--secondary: 210 40% 96.1%;
--secondary-foreground: 222.2 47.4% 11.2%;
Used for accents such as hover effects on <DropdownMenuItem>, <SelectItem>...etc 
--accent: 210 40% 96.1%;
--accent-foreground: 222.2 47.4% 11.2%;
Used for destructive actions such as <Button variant= 
--destructive: 0 100% 50%;
--destructive-foreground: 210 40% 98%;
Used for focus ring 
--ring: 215 20.2% 65.1%;
Border radius for card, input and buttons 
--radius: 0.5rem;

Adding new colors

To add new colors, you need to add them to your CSS file and to your tailwind.config.js file.

app/globals.css 
:root {
  --warning: 38 92% 50%;
  --warning-foreground: 48 96% 89%;
}

.dark {
  --warning: 48 96% 89%;
  --warning-foreground: 38 92% 50%;
}
tailwind.config.js 
module.exports = {
  theme: {
    extend: {
      colors: {
        warning: "hsl(var(--warning))",
        "warning-foreground": "hsl(var(--warning-foreground))",
      },
    },
  },
}

You can now use the warning utility class in your components.

div {
    className = ClassName("bg-warning text-warning-foreground")
}

Other color formats

I recommend using HSL colors for theming but you can also use other color formats if you prefer.

See the Tailwind CSS documentation for more information on using rgb, rgba or hsl colors.

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