'Alle bekannten Farben zurückgeben.
    Private Function ReadKnownColors() As List(Of Color)
        Dim ColorList As New List(Of Color)
        For Each k As KnownColor In [Enum].GetValues(GetType(KnownColor))
            Dim c As Color = Color.FromKnownColor(k)
            If Not c.IsSystemColor Then
                ColorList.Add(c)
            End If
        Next
        Return ColorList
    End Function
 
    'Liefert die am nähesten bekannte Farbe.
    Private Function GetNearestKnownColorName(ByVal col As Color) As String
        Dim Colorlist = ReadKnownColors()
        If Colorlist.Count = 0 Then Return Nothing
        Dim r, g, b As Integer
        r = col.R : g = col.G : b = col.B
        Dim nCol As Color = Nothing
        Dim mDiff As Integer = 10000000
        For Each c In Colorlist
            Dim diff = Math.Abs(c.R - r) + Math.Abs(c.G - g) + Math.Abs(c.B - b)
            If diff < mDiff Then mDiff = diff : nCol = c
        Next
        Return nCol.ToKnownColor.ToString
    End Function

Danke für die Hilfe

Gruß Christian