WPF 利用RichTextBox 打印出不同颜色的文本

using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            WriteLog(Brushes.Red,   "你好！\r\n");
            WriteLog(Brushes.Green, "你好！\r\n");
            WriteLog(Brushes.Blue,  "你好！\r\n");
        }

        private void WriteLog(SolidColorBrush color, string v)
        {
            Run run = new Run() { Text = v, Foreground = color };
            myParagraph.Inlines.Add(run);
        }
    }
}

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="" Width="">
    <Grid>
        <RichTextBox>
            <FlowDocument>
                <Paragraph Name="myParagraph"/>
            </FlowDocument>
        </RichTextBox>
    </Grid>
</Window>