Modifying a Custom Function that is Summing Cells based on Fill Colour

I have a Spreadsheet that i would like to be able to carry out a sum of Range of cells that are equal to a certain colour and also contain no text/numbers. I have come across some code that has created a Function that works perfect for summing the cells of a certain colour. I now need to modify it to also make sure it excluded cells that have text/numbers in them.

This below is what i found online and have used so far.

Function ColorFunction(rColor As Range, rRange As Range, Optional SUM As Boolean)

    Dim rCell As Range

    Dim lCol As Long

    Dim vResult
  

    lCol = rColor.Interior.ColorIndex



    If SUM = True Then

        For Each rCell In rRange

            If rCell.Interior.ColorIndex = lCol Then

                vResult = WorksheetFunction.SUM(rCell, vResult)

            End If

        Next rCell

    Else

        For Each rCell In rRange

            If rCell.Interior.ColorIndex = lCol Then

                vResult = 1 + vResult

            End If

        Next rCell

    End If


   ColorFunction = vResult

End Function