code: public static Color rotateHue (Color color, float fraction) {
  
  		float[] af = Color.RGBtoHSB(color.getRed(), color.getGreen(), color.getBlue(), null);
  
  		float hue = af[0];
  		float saturation = af[1];
  		float brightness = af[2];
  
  		float hueNew = hue  + fraction;
  
  		Color hsb = Color.getHSBColor(hueNew, saturation, brightness);
  		return new Color(hsb.getRed(), hsb.getGreen(), hsb.getBlue(), color.getAlpha());
  	}
docs: Rotate a color through HSB space
  @param color Starting color
  @param fraction Amount to add to the hue. The integer part is discarded to leave a number in [0,1)
  @return