系列のStyleのFillColorおよびStrokeColorプロパティを用いると、積層グラフ（積み上げグラフ）で、棒および外枠（ストローク）の色を個別に設定することができます。

以下に、3つの系列に対してそれぞれ、棒の色を紫／ピンク／黄緑に、棒のストロークの色を青／赤／緑にする例を記載します。

◎サンプルコード（VB）

Imports C1.Chart
Imports C1.Win.Chart
Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' 積層棒グラフのデータ系列の作成
        FlexChart1.BeginUpdate()
        Dim item1 As Series = New Series() With
        {
            .Binding = "Y",
            .BindingX = "X",
            .DataSource = New PointF() {New PointF(1, 1), New PointF(2, 2), New PointF(3, 3)}
        }
        item1.Style.FillColor = Color.Lavender
        item1.Style.StrokeColor = Color.Blue
        item1.Style.StrokeWidth = 2
        Dim item2 As Series = New Series() With
        {
            .Binding = "Y",
            .BindingX = "X",
            .DataSource = New PointF() {New PointF(1, 1), New PointF(2, 1), New PointF(3, 1)}
        }
        item2.Style.FillColor = Color.Pink
        item2.Style.StrokeColor = Color.Red
        item2.Style.StrokeWidth = 2
        Dim item3 As Series = New Series() With
        {
            .Binding = "Y",
            .BindingX = "X",
            .DataSource = New PointF() {New PointF(1, 2), New PointF(2, 2), New PointF(3, 2)}
        }
        item3.Style.FillColor = Color.LightGreen
        item3.Style.StrokeColor = Color.Green
        item3.Style.StrokeWidth = 2
        ' チャートの設定
        FlexChart1.Series.Clear()
        FlexChart1.Series.Add(item1)
        FlexChart1.Series.Add(item2)
        FlexChart1.Series.Add(item3)
        FlexChart1.ChartType = ChartType.Column
        FlexChart1.Stacking = Stacking.Stacked
        FlexChart1.EndUpdate()
    End Sub
End Class

◎サンプルコード（C#）

using System;
using System.Drawing;
using System.Windows.Forms;
using C1.Chart;
using C1.Win.Chart;
namespace _20210312d
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            // 積層棒グラフのデータ系列の作成
            flexChart1.BeginUpdate();
            Series item1 = new Series() {
                Binding="Y",
                BindingX="X",
                DataSource=new PointF[] {new PointF(1,1), new PointF(2, 2) , new PointF(3, 3) }
            };
            item1.Style.FillColor = Color.Lavender;
            item1.Style.StrokeColor = Color.Blue;
            item1.Style.StrokeWidth = 2;
            Series item2 = new Series()
            {
                Binding = "Y",
                BindingX = "X",
                DataSource = new PointF[] { new PointF(1, 1), new PointF(2, 1), new PointF(3, 1) }
            };
            item2.Style.FillColor = Color.Pink;
            item2.Style.StrokeColor = Color.Red;
            item2.Style.StrokeWidth = 2;
            Series item3 = new Series()
            {
                Binding = "Y",
                BindingX = "X",
                DataSource = new PointF[] { new PointF(1, 2), new PointF(2, 2), new PointF(3, 2) }
            };
            item3.Style.FillColor = Color.LightGreen;
            item3.Style.StrokeColor = Color.Green;
            item3.Style.StrokeWidth = 2;
            // チャートの設定
            flexChart1.Series.Clear();
            flexChart1.Series.Add(item1);
            flexChart1.Series.Add(item2);
            flexChart1.Series.Add(item3);
            flexChart1.ChartType = ChartType.Column;
            flexChart1.Stacking = Stacking.Stacked;
            flexChart1.EndUpdate();
        }
    }
}