You can set the color like this:
var serie = Chart_PlanComp.Series.Add("Qtde_Componente");
serie.Color = Color.Green;
Though, setting the font doesn't seem to work...
var serie = Chart_PlanComp.Series.Add("Qtde_Componente");
serie.Font = new Font("Courier New", 15.0f, FontStyle.Italic); //changes nothing
Not even if you set it before adding:
var series = new System.Windows.Forms.DataVisualization.Charting.Series();
series.Font = new Font("Courier New", 15.0f, FontStyle.Italic);
this.chart1.Series.Add(series);
//still nothing