Range.Interior.Color属性返回RGB：

• https://learn.microsoft.com/en-us/office/vba/api/excel.interior.color

因此，在FFFF中，Hex（）的前两个值被跳过。正确的值应该是00FFFF。这可以通过级联技巧实现：
Right("000000" & Hex(Worksheets(1).Cells(1, "A").Interior.Color), 6)
此外，正如@Mathiew Guindon的评论中提到的，VBA中的RGB值are reversed（无论出于何种原因）。然后需要将这两个值进行一次很好的反向。这在HexToRgb()函数中完成：

Sub TestMe()

    Worksheets(1).Cells(1, "A").Interior.Color = vbYellow
    Debug.Print Hex(Worksheets(1).Cells(1, "A").Interior.Color)  'FFFF
    Debug.Print Worksheets(1).Cells(1, "A").Interior.Color       '65535

    Dim hexColor As String
    hexColor = Right("000000" & Hex(Worksheets(1).Cells(1, "A").Interior.Color), 6)

    Debug.Print HexToRgb(hexColor)                               'FFFF00

End Sub

Public Function HexToRgb(hexColor As String) As String

    Dim red As String
    Dim green As String
    Dim blue As String

    red = Left(hexColor, 2)
    green = Mid(hexColor, 3, 2)
    blue = Right(hexColor, 2)

    HexToRgb = blue & green & red

End Function

ffff00是黄色的-https://www.color-hex.com/color/ffff00：

如果您正在阅读或保存字符串中的颜色十六进制代码，即00FF00表示绿色，则以下VBA代码段应将十六进制颜色值转换为VBA颜色值：

//Variables
Dim ColorName as String
Dim ColorValue as long

//Translation
ColorName='00FF00'
ColorValue=Clng("&H" & ColorName)

//Use in the Code
Me.TextBox1.BorderColor=ColorValue

应该可以。