Sub tast()
Dim i As Long
Dim cell As Range
With Sheets(2)
For i = 2 To .Cells(.Rows.Count, 1).End(xlUp).Row
Set cell = Worksheets(1).Columns("A:A").Find _
(What:=.Cells(i, 1).Value, LookIn:=xlFormulas, _
LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
MatchCase:=False, SearchFormat:=False)
If cell Is Nothing Then .Cells(i, 1).Interior.Color = vbYellow
Next i
End With
End Sub
Sub Better()
Dim c As Range
With Sheets(2)
For Each c In Range(.Cells(2, 1), .Cells(.Rows.Count, 1).End(xlUp))
If WorksheetFunction.CountIf(Sheets(1).Columns("A:A"), c) = 0 Then _
c.Interior.Color = vbYellow
Next c
End With