Option Explicit
Sub Suchen()
Dim suche As Range
Dim zaehler As Long
For zaehler = 2 To Workbooks(1).Worksheets(1).Range("G" & Rows.Count).End(xlUp).Row
Set suche = Workbooks(1).Worksheets(2).Range("G2:G" & Workbooks(1).Worksheets(1).Range("G" & Rows.Count).End(xlUp).Row).Find(Workbooks(1).Worksheets(1).Cells(zaehler, 1))
If Not suche Is Nothing Then
Workbooks(1).Worksheets(1).Cells(zaehler, 1).Interior.ColorIndex = 3
End If
Next zaehler
End Sub