Public Class Form1
    Dim WithEvents Pb As New PictureBox With {.Dock = DockStyle.Fill, _
      .BackColor = Color.Black, .Parent = Me}
    Dim rlist As New List(Of Rectangle)({New Rectangle(10, 10, 100, 100), New _
    Rectangle(20, 120, 100, 100), New Rectangle(130, 50, 100, 100)})
    Dim nr As Int32 = -1
 
    Private Sub Pb_MouseDown(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Pb.MouseDown
        For i As Int32 = 0 To rlist.Count - 1
            If rlist(i).Contains(e.Location) Then
                nr = i
                Pb.Invalidate()
            End If
        Next
    End Sub
 
    Private Sub Pb_Paint(sender As Object, e As _
      System.Windows.Forms.PaintEventArgs) Handles Pb.Paint
        For i As Int32 = 0 To rlist.Count - 1
            If nr = i Then
                e.Graphics.FillRectangle(Brushes.Yellow, rlist(i))
            Else
                e.Graphics.FillRectangle(Brushes.White, rlist(i))
            End If
        Next
    End Sub
End Class