Macro to format row color in a range based on text value in column

I would like a macro to automatically (when run) color rows in a range where it begins at $A$3 to $T (the last row will change regularly) based on a text value in column E. The two text values are "CP" and "LG" and I would like to give the "CP" row a color index of 35 and the "LG" rows a color index of 37. I would only like the row to be colored up to the last column in the range "T". Thanks in advance.

I've managed to do it with:

Sub test()
Dim LR As Long, i As Long, c As Long
LR = Range("E" & Rows.Count).End(xlUp).Row
Application.ScreenUpdating = False
For i = 1 To LR
    With Range("E" & i)
        Select Case .Value
            Case "CP": c = 35
            Case "LG": c = 37
            Case Else: c = xlNone
        End Select
        .Offset(, -4).Resize(, 20).Interior.ColorIndex = c
    End With
Next i
Application.ScreenUpdating = True
End Sub

However I would like to have the rows alternate between the color index and white and also avoid formatting the headings row as default which is in row 2. Any ideas?