Option Explicit
Option Compare Text

Sub ertert()
Dim x, i&: Application.ScreenUpdating = False
With Sheets("Incident Management")
 x = .Range("E1:G" & .Cells(Rows.Count, 5).End(xlUp).Row).Value
End With
With CreateObject("Scripting.Dictionary")
 .CompareMode = 1
 For i = 2 To UBound(x)
 .Item(x(i, 1)) = x(i, 3)
 Next i
 
 With Sheets("Open Incidents")
 With .Range("D1:G" & .Cells(Rows.Count, 4).End(xlUp).Row)
 x = .Value
 .Columns(4).Offset(1).Interior.Color = xlNone
 End With
 .Activate
 End With
 
 For i = 2 To UBound(x)
 If .Exists(x(i, 1)) Then
 If .Item(x(i, 1)) <> x(i, 4) Then Cells(i, 7).Interior.ColorIndex = 45
 End If
 Next i
End With
Application.ScreenUpdating = True
End Sub