code: private double doubleValueRightColor( double left, double color ) {
          return rgba( doubleValue( left, red( color ) ), //
                          doubleValue( left, green( color ) ), //
                          doubleValue( left, blue( color ) ), 1 );
      }
docs: Calculate a number on left with a color on the right side. The calculation occur for every color channel.
  
  @param left the left
  @param color the color
  @return color value as long