如何在CollectionView中更改合成布局中的选择颜色

class CustomLayout: UICollectionViewLayout {
    var selectedColor: UIColor = .blue
    
    override func prepare() {
        // 布局的准备工作
        // ...
    }
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let collectionView = collectionView else { return nil }
        
        var attributesArray = [UICollectionViewLayoutAttributes]()
        
        for section in 0..<collectionView.numberOfSections {
            for item in 0..<collectionView.numberOfItems(inSection: section) {
                let indexPath = IndexPath(item: item, section: section)
                let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
                
                // 设置单元格的位置和大小
                // ...
                
                // 根据单元格的选中状态设置颜色
                if collectionView.indexPathsForSelectedItems?.contains(indexPath) == true {
                    attributes.backgroundColor = selectedColor
                } else {
                    attributes.backgroundColor = .clear
                }
                
                attributesArray.append(attributes)
            }
        }
        
        return attributesArray
    }
    
    override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }
}

let layout = CustomLayout()
collectionView.collectionViewLayout = layout