Bmp Image Color Difference

[lchamarthi 2]

I am trying to make a very attractive screen. So i devoloped a good image in 24color bitmap and tried to add to screen. Displayed the message that 24 color bitmap changed to 16color bitmap and accepted in Screen. After downloading to the HMI so much of color difference is there between original bitamap and HMI screen. To make this diff less do anybody suggest a way? i will be thankful if anybody send some standard devoloped images apart from the NS internal Library. Because i am trying for Fan (example) symbol which NS library doesn't have. Can i get sample templates in NS? Thanks in advance