Insert new row creates Run-time error 13 with exisiting simple code

Found code elsewhere, and tweaked it, that allows me to do some simple conditional formatting to alter the colour of a cell in column G depending on the RAG status entry inserted into a cell (Red,Amber,Green,Complete,N/A). The cells in column G have a drop down validation list.

I'm sure that there is a more elegant way of doing this, but it works for me at the moment. However when I insert a row I get an Run-time error '13': Type mismatch message, flagging the

Case "Red"

line of code.

I've tried various things but can't figure it out, but can't get to the bottom of it.

The code is attached below

Private Sub Worksheet_Change(ByVal Target As Range)
Dim icolor As Integer

If Not Intersect(Target, Range("G:G")) Is Nothing Then

Select Case Target

Case "Red"
icolor = 3
Case "red"
icolor = 3
Case "Amber"
icolor = 45
Case "amber"
icolor = 45
Case "Green"
icolor = 4
Case "green"
icolor = 4
Case "Complete"
icolor = 32
Case "complete"
icolor = 32
Case "N/A"
icolor = 15
Case "Not Applicable"
icolor = 15
Case "n/a"
icolor = 15
Case Else

'Whatever

End Select
Target.Interior.ColorIndex = icolor
End If
End Sub

Workbook attached also.