Same as Google's Material Theme Builder, but as a gradle plugin.

Replace all the <version> below with the version shows here.

1. Add gradle plugin

   // "old way"
   buildscript {
       repositories {
           mavenCentral()
       }
       dependencies {
           classpath 'dev.rikka.tools.materialthemebuilder:gradle-plugin:<version>'
       }
   }

   // "new way"
   plugins {
       id 'dev.rikka.tools.materialthemebuilder' version '<version>'
   }

2. Use the plugin in Android application or library module

   plugins {
       id('dev.rikka.tools.materialthemebuilder')
   }
   

3. Config

   materialThemeBuilder {
       // List of themes to generate
       themes {
           // Name of the theme
           theme1 {
               // Primary color, acts as the source color
               primaryColor = "#3F51B5"
               
               // Optional colors, override colors calculated from the source color
               //secondaryColor = "#000000"
               //tertiaryColor = "#000000"
               //neutralColor = "#000000"
               
               // Use dynamic colors on API 31+
               dynamicColors = false
               
               lightThemeFormat = "Theme.Material3.Light.%s"
               lightThemeParent = "Theme.Material3.Light.Rikka"
               darkThemeFormat = "Theme.Material3.Dark.%s"
               darkThemeParent = "Theme.Material3.Dark.Rikka"
           }
           theme2 {
               // ...
           }
       }
   
       // List of extended colors
       extendedColors {
           // Name of the color
           example {
               color = "#000000"
               // Harmonize generated color with primary color
               harmonize = true
           }
       }
   
       // Package name of your application, used in generated class
       packageName = "com.example"
   
       // Optional parts:
   
       // Add Material Design 3 color tokens (such as palettePrimary100) in generated theme
       // rikka.material:material >= 2.0.0 provides such attributes
       // Enable this if your are using rikka.material:material
       generatePalette = false
       
       // Generate Material Design 3 color tokens attributes (such as palettePrimary100)
       // When necessary, you can use this if your are not using rikka.material:material
       generatePaletteAttributes = false
       
       // Generate "textColorOnXxx" attributes such as "textColorOnPrimary", "textColorOnPrimaryHighEmphasis"
       // and "textColorOnPrimaryMediumEmphasis"
       generateTextColors = false
   }

   Harmonize color with dynamic themes:

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
        HarmonizedColors.applyToContextIfAvailable(
            context,
            HarmonizedColorsOptions.Builder()
                .setColorAttributeToHarmonizeWith(R.attr.colorPrimary)
                .setColorAttributes(
                    HarmonizedColorAttributes.create(
                        HarmonizedColorAttributes.createMaterialDefaults().attributes
                            .plus(Harmonization.HARMONIZED_COLOR_ATTRIBUTES)
                    )
                )
            !!.build()
        )
    }