The code implemented looks like this:

If ActiveChart.SeriesCollection(num).Name = "BASEL" Then

ActiveChart.SeriesCollection(num).DataLabels.Selec t

With Selection.Font
.Name = "Arial"
.FontStyle = "Bold"
.Size = 10
.Strikethrough = False
.Superscript = False
.Subscript = False
.OutlineFont = False
.Shadow = False
.Underline = xlUnderlineStyleNone
.ColorIndex = xlAutomatic
.Background = xlAutomatic
End With

ActiveChart.SeriesCollection(num).Select

With Selection.Border
.ColorIndex = 57
.Weight = xlHairline
.LineStyle = xlContinuous
End With

Selection.InvertIfNegative = False
With Selection.Interior
.ColorIndex = 36
.Pattern = xlSolid
End With

End If

The problem is that the progrma does not change the formatting of the label,
but the formatting of the data series bar itself (i.e. changing the colour)
is working perfectly.

Tried different things but didn't come to a solution...