Bonjour,
Un début de réponse à adapter.
Cdlt.
Sub Macro1()
Dim ws As Worksheet
Dim objChart As ChartObject
Dim nb As Long, I As Long
Set ws = ActiveWorkbook.Worksheets("Caster 3")
Set objChart = ws.ChartObjects(1)
nb = objChart.Chart.FullSeriesCollection(1).Points.Count
For I = 1 To nb Step 3
With objChart.Chart.FullSeriesCollection(1)
.Points(I).Format.Fill.ForeColor.RGB = RGB(79, 129, 189)
.Points(I + 1).Format.Fill.ForeColor.RGB = RGB(255, 0, 0)
.Points(I + 2).Format.Fill.ForeColor.RGB = RGB(119, 147, 60)
End With
Next I
Set objChart = Nothing: Set ws = Nothing
End Sub