如何在UICollectionView中更改部分的背景色？

import UIKit

class CustomFlowLayout: UICollectionViewFlowLayout {
    
    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        let attributes = super.layoutAttributesForItem(at: indexPath)
        
        // 判断需要改变背景色的item
        if indexPath.item % 2 == 0 {
            attributes?.backgroundColor = UIColor.red // 设置背景色
        }
        
        return attributes
    }
}

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    
    @IBOutlet weak var collectionView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let customFlowLayout = CustomFlowLayout()
        collectionView.collectionViewLayout = customFlowLayout
        
        // 其他collectionView设置
        collectionView.dataSource = self
        collectionView.delegate = self
    }
    
    // 其他UICollectionViewDataSource和UICollectionViewDelegate方法...
    
}