Thanks Shane and Bob, the code works fine except it does not follow what the
range is saying, the only cell that changes color is O5 and none of the
others react. Below is the final code. Any corrections would be appreciated.

NOTE: I entered additional code to change the font colors as well.


Private Sub Worksheet_Change(ByVal Target As Range)
'-----------------------------------------------------------------
Const WS_RANGE As String = "O5:O43"

On Error Resume Next
If Not Intersect(Target, Me.Range(WS_RANGE)) Is Nothing Then
With Target.Interior
Select Case Target
Case "": .ColorIndex = xlNone
Case 1: .ColorIndex = 3
Case 2: .ColorIndex = 2
Case 3: .ColorIndex = 41
Case 4: .ColorIndex = 6
Case 5: .ColorIndex = 50
Case 6: .ColorIndex = 1
Case 7: .ColorIndex = 46
Case 8: .ColorIndex = 7
Case 9: .ColorIndex = 42
Case 10: .ColorIndex = 13
Case 11: .ColorIndex = 48
Case 12: .ColorIndex = 4
End Select
End With
End If

On Error Resume Next
If Not Intersect(Target, Me.Range(WS_RANGE)) Is Nothing Then
With Target.Font
Select Case Target
Case "": .ColorIndex = xlNone
Case 1: .ColorIndex = 2
Case 2: .ColorIndex = 1
Case 3: .ColorIndex = 2
Case 4: .ColorIndex = 1
Case 5: .ColorIndex = 6
Case 6: .ColorIndex = 6
Case 7: .ColorIndex = 1
Case 8: .ColorIndex = 1
Case 9: .ColorIndex = 1
Case 10: .ColorIndex = 2
Case 11: .ColorIndex = 3
Case 12: .ColorIndex = 1

End Select
End With
End If
ws_exit:
Application.EnableEvents = True
End Sub