Assuming your third column is column "C" and that you would want to change
the colors of the XY points based on the names Jim, Frank, or Kim, a VBA
option could look like this (does not include any error handling):

Sub ChangeXYColors()
   Application.ScreenUpdating = False
   Dim Rng As Range
   Cnt = 1
   For Each Rng In Range("C2:C10")
   ActiveSheet.ChartObjects("Chart1").Activate
   ActiveChart.SeriesCollection(1).Points(Cnt).Select
       If Rng.Value = "Jim" Then
           With Selection
               .MarkerBackgroundColorIndex = 10
               .MarkerForegroundColorIndex = 10
           End With
       ElseIf Rng.Value = "Frank" Then
           With Selection
               .MarkerBackgroundColorIndex = 11
               .MarkerForegroundColorIndex = 11
           End With
       ElseIf Rng.Value = "Kim" Then
           With Selection
               .MarkerBackgroundColorIndex = 12
               .MarkerForegroundColorIndex = 12
           End With
       End If
   Cnt = Cnt + 1
   Next Rng
ActiveChart.Deselect
End Sub