Setting Fill color for Textboxes

I have the code below to set the color for my text boxes, but my problem is that I can't find the right code for what I want for my SchemeColor. I've looked online at all the listings of colors in Excel (including here: http://dmcritchie.mvps.org/excel/colors.htm), and the codes don't match up with my experience. For instance, light gray is supposed to be 15, but when I replace 1 with 15, my textboxes turn aqua. The closest I've come is by putting 1, and I've ascertained that there are 80 possible values, but trial and error is no way to find the right code. What I want is a very light gray, say 5% gray, just enough to stand out from the white background. Any help on this is greatly appreciated.

Sub FormatTextboxes()
    Dim ws As Worksheet
    Dim shp As Shape
    
    For Each ws In ActiveWorkbook.Worksheets
        For Each shp In ws.Shapes
            If shp.Type = msoTextBox Then
                With shp
                    .Fill.ForeColor.SchemeColor = 1
                    .Fill.ForeColor.TintAndShade = -0.2
                    .Shadow.Type = msoShadow5
                End With
            End If
        Next
    Next
End Sub