This snippet might help you make a Material Design 3 theme for your Jetpack Compose app

Theme.kt

package my.awesome.package // put your package name here

import android.app.Activity
import android.os.Build
import androidx.compose.foundation.isSystemInDarkTheme
import androidx.compose.material3.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.SideEffect
import androidx.compose.ui.graphics.toArgb
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.platform.LocalView
import androidx.core.view.WindowCompat

// you might want to try
// https://m3.material.io/theme-builder
// for generating a Material Design 3 palette

private val LightColorScheme = lightColorScheme(
  // your light color scheme colors
)

private val DarkColorScheme = darkColorScheme(
  // your dark color scheme colors
)

@Composable
fun MyAwesomeTheme( // put your theme name here
  useDarkTheme: Boolean = isSystemInDarkTheme(),
  useDynamicColor: Boolean = true,
  content: @Composable () -> Unit,
) {
  val colorScheme = when {
    useDynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
      val context = LocalContext.current
      if (useDarkTheme) dynamicDarkColorScheme(context)
      else dynamicLightColorScheme(context)
    }
    useDarkTheme -> DarkColorScheme
    else -> LightColorScheme
  }
  val view = LocalView.current
  if (!view.isInEditMode) {
    SideEffect {
      val window = (view.context as Activity).window
      val insets = WindowCompat.getInsetsController(window, view)
      window.statusBarColor = colorScheme.whatever.toArgb() // choose a status bar color
      window.navigationBarColor = colorScheme.whatever.toArgb() // choose a navigation bar color
      insets.isAppearanceLightStatusBars = !useDarkTheme
      insets.isAppearanceLightNavigationBars = !useDarkTheme
    }
  }
  MaterialTheme(
    colorScheme = colorScheme,
    typography = Typography,
    content = content,
  )
}