Checking on properties of a sequence of cards

CardQuestions.scala

object CardQuestions {

  case class Card(number: Int, color: String)

  val cards = Seq(
    Card(5, "red"),
    Card(7, "red"),
    Card(3, "black"))

  // Do the cards all have the same color?
  def haveSameColor(cards: Seq[Card], ifEmpty: Boolean = true): Boolean = {
    ???
  }

  // Do the cards all have the same number?
  def haveSameNumber(cards: Seq[Card], ifEmpty: Boolean = true): Boolean = {
    ???
  }
  
}