从工作表函数传递范围时获取单元格内部颜色失败

我正在尝试编写一个可以从一个单元格调用的简单函数，如果给定单元格的背景具有特定的背景颜色，则该函数将返回。

从子例程调用时，此函数按预期工作，但从工作表调用时，此函数失败。在生产线上

IntColor = Cell.DisplayFormat.Interior.Color

这是所有代码

Option Explicit

Public Function GetCellRGB(Rng As Range) As Integer()
    Dim Result(1 To 3) As Integer
    Dim Cell As Range
    Set Cell = Rng.Cells(1, 1)

    Dim IntColor As Integer

    ' when called from worksheet, function exits here with a #VALUE error
    IntColor = Cell.DisplayFormat.Interior.Color

    Result(1) = IntColor Mod 256 ' red
    Result(2) = IntColor \ 256 Mod 256 ' green
    Result(3) = IntColor \ 65536 Mod 256 ' blue

    GetCellRGB = Result
End Function

Public Function IsColor(Rng As Range, R As Integer, G As Integer, B As Integer) As Boolean
    Dim Vals() As Integer

    Vals = GetCellRGB(Rng)
    If R = Vals(1) And G = Vals(2) And B = Vals(3) Then
        IsColor = True
    Else
        IsColor = False
    End If
End Function

' This works as expected
Sub ColorTest()
    Dim Rng As Range
    Set Rng = ThisWorkbook.ActiveSheet.Range("A1")
    Debug.Print IsColor(Rng, 255, 0, 0)
End Sub