title: Unresolved reference: Color
body: <p>Why did this error happen?
  It's very simple code.
  Should I use capital letters?</p>
  
  <pre><code>fun getMnemonic(color: Color) = when (color) {   
  
      color.RED -&gt; "Richard"   
      color.ORANGE -&gt; "Of" 
      color.YELLOW -&gt; "York" 
      color.GREEN -&gt; "Gave" 
      color.BLUE -&gt; "Battle" 
      color.INDIGO -&gt; "In" 
      color.VIOLET -&gt; "Vain" 
      else -&gt; println("ok retry") 
  }    
  
  fun main() {
      println(getMnemonic(color.BLUE))
  }      
  </code></pre>
  
  <p>Error message is:
  Unresolved reference: Color</p>