public boolean isValid() {
    return (mPrimaryColor != mPrimaryTextColor) && (mPrimaryDarkColor != mPrimaryTextColor);
  }
@Test
  public void isNotValidIfTextIsSame() {
    Assert.assertFalse(overlay(Color.GRAY, Color.GRAY, Color.GRAY).isValid());
    Assert.assertFalse(overlay(Color.BLACK, Color.BLUE, Color.BLACK).isValid());
    Assert.assertFalse(overlay(Color.MAGENTA, Color.WHITE, Color.WHITE).isValid());
  }