Gimp - where to change the color of opaque

[Uhu]

Sorry guys to open such treads, but found nothing on net about this.
So, when I edit a PanzerCorps png in Gimp it's a great thing, but Gimp changes the black opaque-background to white. Which is mostly no problem, but sometime it is.
Can somebody tell me please, where can I set it to black in Gimp setup?

Thanks

[huertgenwald]

With the opacity slider in the toolboxes ?

[Uhu]

Thanks for the tipp! But apparently another solution turned out: when I at "save as" the option"saving backgorunds" not choose, than it will no white opacity background saved.

With the opacity slider in the toolboxes ?

[Wargamer74]

Another tip is to make sure the background is set to transparent. Go to layers>transparency>Add Alpha Channel, after this you should be able save it with the default png settings.