Colors

The colors property in your target configuration allows you to define custom color assets that are added to the target’s Assets.xcassets. These colors can be used in your Swift code and support both light and dark mode.

Basic Usage

Define colors in your expo-target.config.js:

module.exports = {
  type: "widget",
  colors: {
    // Simple color (used in both light and dark mode)
    primary: "#FF0000",
    
    // Dynamic color with light and dark variants
    secondary: {
      light: "#FF0000",
      dark: "#0000FF"
    },
    
    // Special colors for widgets
    $accent: "steelblue",
    $widgetBackground: "dodgerblue"
  }
};

Color Formats

Simple Colors

Provide a CSS color string for a color that looks the same in light and dark mode:

colors: {
  primary: "#FF0000",
  secondary: "rgb(255, 0, 0)",
  accent: "red",
  brand: "steelblue"
}

Supported formats:

Hex: "#FF0000", "#F00"
RGB: "rgb(255, 0, 0)"
RGBA: "rgba(255, 0, 0, 0.5)"
Named colors: "red", "blue", "steelblue", etc.

Dynamic Colors

Provide separate colors for light and dark appearance:

colors: {
  background: {
    light: "#FFFFFF",
    dark: "#000000"
  },
  text: {
    light: "#000000",
    dark: "#FFFFFF"
  }
}

light

string

required

The color to use in light mode.

dark

string

The color to use in dark mode. If omitted, the light color is used in both modes.

Using Colors in Swift

Colors are accessible as named assets in SwiftUI and UIKit:

SwiftUI
UIKit

import SwiftUI

struct MyWidgetView: View {
    var body: some View {
        VStack {
            Text("Hello")
                .foregroundColor(Color("primary"))
            
            Rectangle()
                .fill(Color("background"))
        }
    }
}

import UIKit

let primaryColor = UIColor(named: "primary")
let backgroundColor = UIColor(named: "background")

view.backgroundColor = backgroundColor
label.textColor = primaryColor

Colors automatically adapt to the user’s appearance settings (light/dark mode) when using dynamic colors.

Special Color Names

Certain color names have special meanings and are mapped to Xcode build settings:

Name	Build Setting	Purpose
`$accent`	`ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME`	Sets the global accent color. In widgets, this is used for the tint color of buttons when editing the widget.
`$widgetBackground`	`ASSETCATALOG_COMPILER_WIDGET_BACKGROUND_COLOR_NAME`	Sets the background color of the widget.

$accent

The global accent color is used throughout your extension. For widgets, it’s particularly important as it tints interactive elements in the widget configuration interface.

colors: {
  $accent: "steelblue"
  // or with dark mode
  $accent: {
    light: "steelblue",
    dark: "lightblue"
  }
}

SwiftUI:

// Access via the Color.accentColor property
Button("Edit") { }
    .tint(.accentColor)

$widgetBackground

The widget background color sets the default background for your widget. This is primarily used by widget configuration interfaces.

colors: {
  $widgetBackground: "dodgerblue"
  // or with dark mode
  $widgetBackground: {
    light: "#E0F7FF",
    dark: "#1A1A2E"
  }
}

Note: You can still override these colors in your Swift code, but setting them via build settings ensures consistency and proper integration with the widget configuration UI.

Color Assets Generation

When you run expo prebuild, the plugin automatically:

Creates an Assets.xcassets directory in your target
Generates a .colorset subdirectory for each color
Creates a Contents.json file with the color definitions
Converts CSS color strings to display-P3 color space
Configures the appropriate Xcode build settings for special colors

The generated structure looks like this:

targets/
  MyWidget/
    Assets.xcassets/
      primary.colorset/
        Contents.json
      background.colorset/
        Contents.json
      $accent.colorset/
        Contents.json

Color Space

Colors are generated using the display-P3 color space by default, which provides a wider color gamut than sRGB and is the standard for Apple devices. The conversion from CSS colors to display-P3 is handled automatically. Colors are defined with RGBA components ranging from 0.0 to 1.0.

TypeScript Type Definitions

type DynamicColor = {
  light: string;
  dark?: string;
};

type ColorConfig = Record<string, string | DynamicColor>;

Complete Example

Here’s a complete example showing how to define and use colors in a widget:

Config
Swift

// targets/MyWidget/expo-target.config.js
module.exports = {
  type: "widget",
  colors: {
    // Brand colors
    primary: "#007AFF",
    secondary: "#5AC8FA",
    
    // Dynamic colors
    background: {
      light: "#FFFFFF",
      dark: "#1C1C1E"
    },
    cardBackground: {
      light: "#F2F2F7",
      dark: "#2C2C2E"
    },
    text: {
      light: "#000000",
      dark: "#FFFFFF"
    },
    secondaryText: {
      light: "#3C3C43",
      dark: "#EBEBF5"
    },
    
    // Widget-specific
    $accent: "#007AFF",
    $widgetBackground: {
      light: "#F2F2F7",
      dark: "#1C1C1E"
    },
    
    // Gradient colors
    gradient1: "#FF6B6B",
    gradient2: "#4ECDC4"
  }
};

import SwiftUI
import WidgetKit

struct MyWidgetView: View {
    var entry: Provider.Entry
    
    var body: some View {
        ZStack {
            // Background adapts to light/dark mode
            Color("background")
            
            VStack(spacing: 12) {
                // Card with dynamic background
                VStack(alignment: .leading, spacing: 8) {
                    Text("Title")
                        .font(.headline)
                        .foregroundColor(Color("text"))
                    
                    Text("Subtitle")
                        .font(.subheadline)
                        .foregroundColor(Color("secondaryText"))
                }
                .padding()
                .background(Color("cardBackground"))
                .cornerRadius(12)
                
                // Gradient using custom colors
                LinearGradient(
                    colors: [Color("gradient1"), Color("gradient2")],
                    startPoint: .leading,
                    endPoint: .trailing
                )
                .frame(height: 4)
                
                // Button uses accent color
                Button(intent: MyIntent()) {
                    Label("Action", systemImage: "star.fill")
                }
                .tint(Color("primary"))
            }
            .padding()
        }
    }
}

Best Practices

Always Support Dark Mode

Provide dark mode variants for better user experience:

colors: {
  background: {
    light: "#FFFFFF",
    dark: "#000000"
  }
}

Use Semantic Names

Name colors based on their purpose, not their appearance:

// Good
colors: {
  background: "#FFFFFF",
  text: "#000000",
  error: "#FF0000"
}

// Avoid
colors: {
  white: "#FFFFFF",
  black: "#000000",
  red: "#FF0000"
}

Maintain Contrast

Ensure sufficient contrast between foreground and background colors for accessibility:

colors: {
  background: { light: "#FFFFFF", dark: "#000000" },
  text: { light: "#000000", dark: "#FFFFFF" }  // High contrast
}

Always define $accent and $widgetBackground for widgets:

colors: {
  $accent: "#007AFF",
  $widgetBackground: { light: "#F2F2F7", dark: "#1C1C1E" }
}

Troubleshooting

Colors not showing up

Make sure you’ve run expo prebuild after adding colors
Check that the color name is correctly spelled in Swift
Verify the Assets.xcassets directory exists in your target folder

Colors look wrong in dark mode

Ensure you’ve provided a dark variant
Test on an actual device or simulator with dark mode enabled
Check the color values in the generated Contents.json files

Accent color not working

Make sure you’re using $accent (with the $ prefix)
Verify the ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME build setting is set
Check that the colorset was generated in Assets.xcassets

CLI

API

Targets

Basic Usage

Color Formats

Simple Colors

Dynamic Colors

Using Colors in Swift

Special Color Names

$accent

$widgetBackground

Color Assets Generation

Color Space

TypeScript Type Definitions

Complete Example

Best Practices

Always Support Dark Mode

Use Semantic Names

Maintain Contrast

Set Widget Colors

Troubleshooting

Colors not showing up

Colors look wrong in dark mode

Accent color not working

Build docs developers (and LLMs) love

CLI

API

Targets

Documentation Index

​Basic Usage

​Color Formats

​Simple Colors

​Dynamic Colors

​Using Colors in Swift

​Special Color Names

​$accent

​$widgetBackground

​Color Assets Generation

​Color Space

​TypeScript Type Definitions

​Complete Example

​Best Practices

​Always Support Dark Mode

​Use Semantic Names

​Maintain Contrast

​Set Widget Colors

​Troubleshooting

​Colors not showing up

​Colors look wrong in dark mode

​Accent color not working

Build docs developers (and LLMs) love

Basic Usage

Color Formats

Simple Colors

Dynamic Colors

Using Colors in Swift

Special Color Names

$accent

$widgetBackground

Color Assets Generation

Color Space

TypeScript Type Definitions

Complete Example

Best Practices

Always Support Dark Mode

Use Semantic Names

Maintain Contrast

Set Widget Colors

Troubleshooting

Colors not showing up

Colors look wrong in dark mode

Accent color not working