一般UICollectionView点击后会显示默认的透明色，希望修改为特定的颜色，最终发现是设置背景色的view设置错了，应该是：[cell.contentView setBackgroundColor:[UIColor redColor]];
具体代码如下：

- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}
- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];
    //设置(Highlight)高亮下的颜色
    [cell.contentView setBackgroundColor:[UIColor redColor]];
}

- (void)collectionView:(UICollectionView *)collectionView  didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];
    //设置(Nomal)正常状态下的颜色
    [cell.contentView setBackgroundColor:[UIColor blueColor]];
}

需要注意：是cell.contentView的背景颜色。