Change colour of chart series with VBA

Hi
unfortunately your combo box links to a file on your C:\ drive, so I can't see how it works exactly.
assuming your combobox links to a range containing colours, and the first of these cells is the blue you want to replace (as on your second sheet) then assuming your colour range has the name "ColRange", and the output cell is names OutRange, try this

Sub ColChange()
Dim ss, MyCol, Bcol
MyCol = Range("ColRange").Cells(Range("Outrange").Value).Interior.Color
Bcol = Range("ColRange").Cells(1).Interior.Color

For Each ss In ActiveChart.SeriesCollection
    If ss.Format.Line.ForeColor.RGB = Bcol Then ss.Format.Line.ForeColor.RGB = MyCol
Next ss
End Sub