Configuring the highlight of a list collectionView cell

In a collection view I want that when a cell is tapped to have the background color changed to indicate highlighting. When that same cell is tapped again, turn the highlighting off. When another cell is tapped, un-highlight the previously highlighted cell and highlight the new one.

I pretty much have that working but it's all done manually in code. If there's a better way using delegate methods or something, please enlighten me.

The collection view is in a pop-up view. My problem is that when the pop-up view is closed and then reopened, the last selected cell is still highlighted.

I tried this, but no-joy.

choose_CollectionView_Outlet.indexPathsForSelectedItems?.forEach { choose_CollectionView_Outlet.deselectItem(at: $0, animated: false) }

I think it's because I am manually setting the background color to indicate highlight. If anybody has a solution for this, please share it.

extension Choose_Items_VC: UICollectionViewDelegate
{
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
    {
        if collectionView == collectionView_Outlet
        {
            // Filter Selection
            let item = itemArray[indexPath.row].Item_Name
            
            if let cell = collectionView.cellForItem(at: indexPath)
            {
                cell.backgroundColor = .lightGray
            }
            
            switch itemPicked
            {
            case K.AppFacing.type:
                if item == type_Fld_Outlet.text
                {
                    pickerDoneBtn_Outlet.isEnabled = false
                    pickerFld_Outlet.text = ""
                    newType_ID = 0
                } else {
                    pickerFld_Outlet.text = item
                    newType_ID = itemArray[indexPath.row].ItemID
                    pickerDoneBtn_Outlet.isEnabled = true
                }
                
            case K.AppFacing.style:
                if item == style_Fld_Outlet.text
                {
                    pickerDoneBtn_Outlet.isEnabled = false
                    pickerFld_Outlet.text = ""
                    newType_ID = 0
                } else {
                    pickerFld_Outlet.text = item
                    newType_ID = itemArray[indexPath.row].ItemID
                    pickerDoneBtn_Outlet.isEnabled = true
                }
                
            case K.AppFacing.venue:
                if item == venue_Fld_Outlet.text
                {
                    pickerDoneBtn_Outlet.isEnabled = false
                    pickerFld_Outlet.text = ""
                    newType_ID = 0
                } else {
                    pickerFld_Outlet.text = item
                    newType_ID = itemArray[indexPath.row].ItemID
                    pickerDoneBtn_Outlet.isEnabled = true
                }
                
            default: break
            }
        } else if collectionView == choose_CollectionView_Outlet {
            let cell = collectionView.cellForItem(at: indexPath)
            
            if cell?.backgroundColor == .lightGray
            {
                cell?.backgroundColor = nil
                // cell?.isSelected = false
                // cell?.isHighlighted = false
                add_Btn_Outlet.isEnabled = false
                gItem_ID = 0
            } else {
                cell?.backgroundColor = .lightGray
                // cell?.isSelected = true
                // cell?.isHighlighted = true
                gItem_ID = choose_Items_Array[indexPath.item].ItemID
                add_Btn_Outlet.isEnabled = true
            }
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath)
    {
        if let cell = collectionView.cellForItem(at: indexPath)
        {
            if collectionView == collectionView_Outlet
            {
                cell.backgroundColor = .lightGray
            }
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath)
    {
        if let cell = collectionView.cellForItem(at: indexPath)
        {
            if collectionView == collectionView_Outlet
            {
                cell.backgroundColor = nil
            }
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath)
    {
        if let cell = collectionView.cellForItem(at: indexPath)
        {
            cell.backgroundColor = nil
        }
    }
}