UnicornHello.scala

trait Greeter {
  def greet(who: String): String =
    s"hello, $who"
}

import scala.io.AnsiColor._

object Colorful {
  def endlessRainbow: Stream[String] = RED #:: YELLOW #:: GREEN #:: CYAN #:: BLUE #:: endlessRainbow
}

trait Colorful {
  import Colorful._
  def colorize(message: String): String =
    endlessRainbow.
      zip(message).
      flatMap {
        case (color: String, char: Char) => s"$color$char"
      }.mkString ++ RESET
}

trait ColorfulGreeter extends Colorful with Greeter {
  val colorfulGreeting = greet _ andThen colorize _
}

object UnicornHello extends App with ColorfulGreeter {
  println(colorfulGreeting("world"))
}