colors.kt

fun Context.attributeColorWithAlpha(
  @AttrRes overlayColorAttributeResId: Int,
  @FloatRange(from = 0.0, to = 1.0) overlayAlpha: Float
): Int {
  val surfaceColor = MaterialColors.getColor(this, R.attr.colorSurface, "Color surface not found")
  val colorWithAlpha = MaterialColors.getColor(this, overlayColorAttributeResId, "Color attribute not found").let {
    MaterialColors.compositeARGBWithAlpha(it, (255 * overlayAlpha).roundToInt())
  }
  return MaterialColors.layer(surfaceColor, colorWithAlpha)
}

demo.kt

val error8Alpha = context.attributeColorWithAlpha(R.attr.colorError, 0.08f)
val success50Alpha = context.attributeColorWithAlpha(R.attr.success, 0.5f)