Nigel,

I adjusted the code and it seems to be working now. Don't know if it's ideal since it is going to check through cell D1000 every time, but it's definitely recognizing yellow cells beyond the first row

Sub test()
Dim rng As range
Set rng = Sheets("Sheet1").range("A1:DD1000")


With rng
    For Each cell In rng
        If cell.Interior.ColorIndex = 6 Then
            If cell.Value = Empty Then
                MsgBox "Please ensure that you have filled      " & Chr(10) & "out all empty yellow fields'.", vbOKOnly + vbInformation, "Please fill empty fields"
                Exit Sub
            End If
        End If
    Next cell
End With
End Sub
Thank you for helping with this!