Here is how to start (then it's up to you)
Code:
Sub SA_col()
Dim oSA As SmartArt
Dim L As Long
'smart art must be selected!
Set oSA = ActiveWindow.Selection.ShapeRange(1).SmartArt
For L = 1 To oSA.AllNodes.Count
Select Case oSA.AllNodes(L).Level
Case Is = 1
oSA.AllNodes(L).Shapes(1).Fill.ForeColor.RGB = RGB(0, 0, 255) 'blue
Case Is = 2
oSA.AllNodes(L).Shapes(1).Fill.ForeColor.RGB = RGB(0, 255, 0) 'green
'etc for other levels
End Select
Next L
End Sub