如果直接采用    

   self.searchBar.backgroundColor = [UIColor redColor];

   self.searchBar.tintColor = [UIColor redColor];

可能会达不到预想的效果，所以就得采用其他方案了。

先看UISearchBar的层级结构，SearchBar里面包含的view下有三个控件，分别是“UIImageView类型的UISearchBarBackgroud”、“UITextField类型的UISearchBarTextField”、“UIButton类型UINavigationButton”，所以就可以采用遍历循环获取到UISearchBar内层的视图，依次进行修改

UISearchBar的层级结构

代码

for (UIView *view in self.searchController.searchBar.subviews.lastObject.subviews) {

    if([view isKindOfClass:NSClassFromString(@"UISearchBarBackground")]) {

            UIImageView*viewSearch = (UIImageView*)view;

            viewSearch.image= [UIImagecreateImageWithColor:[UIColorwhiteColor]];

    }else if ([view isKindOfClass:NSClassFromString(@"UISearchBarTextField")]){

            UITextField*textField = (UITextField*)view;

            textField.backgroundColor=  UIColorFromRGB(0xF5F5F5);

}else if ([view isKindOfClass:NSClassFromString(@"UINavigationButton")]){

            UIBotton*botton = (UIBotton*)view;

    }

 }