Finding Cells Colored By Conditional Formatting

This works if a cell is simply formatted "red" but it does not work if the same cell is colored "red" by virture of conditional formatting. How do I find cells that have been set to color "red" by conditional formatting

This prevents saving the workbook without entering all the data.
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Dim Row As Integer
Dim Col As Integer
For Row = 1 To 450
For Col = 1 To 50
If Worksheets("Sheet1").Cells(Row, Col).Interior.Color = RGB(255, 0, 0) Then
MsgBox "Every cell must have data."
Cancel = True
End If
Next Col
Next Row
End Sub