code: static double rgba( double r, double g, double b, double a ) {
          return Double.longBitsToDouble( Math.round( a * 0xFFFF ) << 48 | (colorLargeDigit(r) << 32) | (colorLargeDigit(g) << 16) | colorLargeDigit(b) );
      }
docs: Create a color from rgba values
  @param r red in range of 0 to 255.0
  @param g green in range of 0 to 255.0
  @param b blue in range of 0 to 255.0
  @param a alpha in range of 0.0 to 1.0
  @return color value as long