White bg in logo.png?

I replaced the drupal logo.png with a custom graphic. But my custom png still shows up with a white bg, even though made it transparent, against the blue current1.gif. Can u tell me how to make the logo.png have the same blue color as current1.gif? Do i need to set the bg of my custom logo.png to the same color?

thanks, sorry if this is a really dumb question
-A