僅用于顏色切換，您只需要單擊的PictureBox。它存儲在sender參數(shù)中。

如果你想要坐標，你需要在PictureBox上存儲一些信息。您不想指定50個處理程序。我的做法是：；使用控件的Tag屬性。

您的for-loop應該是：

for (int cols = 0; cols < COLUMNS; cols++)
{
    for (int rows = 0; rows < ROWS; rows++)
    {                    
        PictureBox newPic = new PictureBox();
        newPic.Height = HEIGHT;
        newPic.Width = WIDTH;
        newPic.BackColor = Color.Maroon;

        // instead of the coordinates, store the indices (for col, row)
        newPic.Tag = new Point(cols, rows);

        // I would use the Width on the cols, instead of the Height.
        int x = cols * (WIDTH + SPACE); 
        int y = rows * (HEIGHT + SPACE);
        newPic.Location = new Point(x + SPACE, y + SPACE);
        newPic.Click += NewPic_Click;

        items.Add(newPic);
        this.panel2.Controls.Add(newPic);

    }
}

你的處理程序應該是這樣的：

// a field to store the previous selected picturebox.
private PictureBox _currentPictureBox = null;

private void NewPic_Click(object sender, EventArgs e)
{
    // the picturebox which has been clicked, is stored in the sender object, but you need to cast it to a PictureBox.
    PictureBox pb = (PictureBox)sender;

    // just for the extra use of the Tag.
    var location = (Point)pb.Tag;
    // location.X Contains the Column index
    // location.Y Contains the Row index



    // did we have a previous picturebox?
    if(_currentPictureBox != null)
    {
        // change the previous pictureBox back to Maroon
        _currentPictureBox.BackColor = Color.Maroon;
    }

    // change the current to blue
    pb.BackColor = Color.Blue;

    // store the new one as the current. (so we can revert it)
    _currentPictureBox = pb;
}

我沒有測試過，只是在記事本上。所以可能有一些拼寫錯誤。但我希望你能理解。