title: What should be the color of the Ripple, colorPrimary or colorAccent? (Material Design)
body: <p>I have reading <a href="http://www.google.com/design/spec/material-design/introduction.html" rel="noreferrer">Material Design Guidelines</a> but I don't know what should be the color of the Ripple if it isn't black (with alpha).</p>
  
  <p>For example, I have an app with colorPrimary = blue, and colorAccent = red. Actually I am using the colorAccent (with alpha), I should use colorPrimary (with alpha) if I want a color different of black to the ripple?</p>
  
  <p>I checked all app of Google but they never use ripples with color.</p>
  
  <p>An image like I have now:</p>
  
  <p><img src="https://i.stack.imgur.com/N1roz.png" alt="ripple"></p>