Dim ColorList As New List(Of Color)
 
  'Alle bekannten Farben in die ColorList eintragen.
  Sub ReadKnownColors()
    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
  End Sub
 
  'Liefert die am nähesten bekannte Farbe.
  Function GetNearestKnownColor(col As Color) As Color
    If ColorList.Count = 0 Then Return Nothing
    Dim r, g, b As Integer
    r = col.R : g = col.G : b = col.B
 
    Dim Q = From c In ColorList
            Let diff = Math.Abs(c.R - r) + Math.Abs(c.G - g) + Math.Abs(c.B - b)
            Order By diff
            Select c
 
    Return Q.First
  End Function