Can you use VLookup with ColorFunction?

Try this macro to do the colouring.

Sub Test()
For N = 6 To Cells(Rows.Count, 1).End(xlUp).Row
    For M = 5 To Cells(N, Columns.Count).End(xlToLeft).Column
        If Cells(N, M) = WorksheetFunction.Min(Range(Cells(N, 5), Cells(N, Columns.Count).End(xlToLeft))) Then
            Cells(N, M).Interior.ColorIndex = Cells(4, M).Interior.ColorIndex
            Exit For
        End If
    Next M
Next N
End Sub