Option Explicit
Dim N As Integer
Dim J As Integer

Private Sub Form_Click()
Dim pic As PictureBox

    For Each pic In Me.Controls
        pic.BackColor = Me.BackColor
    Next
    Set pic = Nothing
    
    If N = J Then
        N =  0 
    End If
    N = N +  1 
    Me.pic_mus N

End Sub

Friend Function pic_mus(ByVal N As Integer)
Dim ctl As Control
Dim pic As PictureBox

Set ctl = Me.Controls("Picture" & N)
If TypeOf ctl Is PictureBox Then
    Set pic = ctl
    Debug.Print pic.Name
    pic.BackColor = VBRUN.ColorConstants.vbGreen
End If

Set ctl = Nothing
Set pic = Nothing

End Function

Private Sub Form_Load()
Dim pic As PictureBox

    N =  0 
    J =  0 
    For Each pic In Me.Controls
        J = J +  1 
    Next
    Set pic = Nothing
    
End Sub