how change appbar background color with sliverappbar - Flutter

Question

How can I change the color in the video to white?

SliverAppBar(
              backgroundColor: Colors.white,
              pinned: true,
              stretch: true,
              leading: IconButton(onPressed: () {  }, icon: const Icon(Icons.ac_unit_rounded),),
              stretchTriggerOffset: 30,
              onStretchTrigger:() => Future.value(true),
              actions: [
                IconButton(onPressed: () {  }, icon: const Icon(Icons.ac_unit_rounded),)
              ],
              expandedHeight: 125.0,
              flexibleSpace: FlexibleSpaceBar(
                title: Container(width: 250,height: 25,decoration: BoxDecoration(color: Colors.lightGreen),),
                centerTitle: true,
                stretchModes:const <StretchMode> [
                  StretchMode.zoomBackground
                ],
                background: const Image(image: AssetImage('assets/images/nuriskin.png')),
              ),
            ),

I changed the colors in the theme, but that color didn't change