Opera Browser Default Settings

[Vernon]

I am using Windows XP (with service pack 2) operating system & every time I open the Opera Browser, it changes my display setting from 16 bit to 8 bit which displays poor color quality. I can then go to my Control Panel display setting and change it back to 16 bit OK, which will work until I close out the browser, but it then changes it back to 8 bit every time I open the Opera Browser again. How do I configure the Opera Browser to set the default color quality to 16 bit instead of 8 bit when opening the browser?