Kotlin - Enum with any object example

anyObjectEnumExample.kt

enum class Color {
    RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET
}

fun mix(firstColor: Color, secondColor: Color) =
        when (setOf(firstColor, secondColor)) {
            setOf(Color.RED, Color.YELLOW) -> Color.ORANGE
            setOf(Color.YELLOW, Color.BLUE) -> Color.GREEN
            setOf(Color.BLUE, Color.VIOLET) -> Color.INDIGO
            else -> throw Exception("bla color")
        }

fun main(args: Array<String>) {
    println(mix(Color.YELLOW, Color.BLUE))
    // GREEN
}