试试这个：

<TextBlock Text="#FF84312F">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Setter Property="Foreground" Value="{Binding Text,RelativeSource={RelativeSource Self}}" />
        </Style>
    </TextBlock.Style>
</TextBlock>

或者这样：

<TextBlock Text="#FF84312F">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Style.Triggers>
                <Trigger Property="Text" Value="#FF84312F">
                    <Setter Property="Foreground" Value="{Binding Text,RelativeSource={RelativeSource Self}}" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

它会无条件或有条件地（使用Trigger）将Foreground设定为Text属性所指定的值。

注意事项：

此答案基于answer provided by mm8的注解
可以使用转换器将字符串转换为SolidColorBrush：

转换器类：

public class TextToSolidColorBrushConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var color = Brushes.Black;
        try
        {
            var converted = new BrushConverter().ConvertFromString(value?.ToString());
            color = converted != null ? (SolidColorBrush) converted : Brushes.Black;
        }
        catch (Exception e)
        {
            // ignored
        }
        return color;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

XAML文件：

<Window.Resources>
    <local:TextToSolidColorBrushConverter x:Key="TextToSolidColorBrushConverter"/>
</Window.Resources>

<TextBlock Text="Any text">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Setter Property="Foreground" Value="{Binding Text,RelativeSource={RelativeSource Self}, Converter={StaticResource TextToSolidColorBrushConverter}}" />
        </Style>
     </TextBlock.Style>
</TextBlock>

根据您的意见：

我想要的是。我必须检查文本块文本，如果文本块文本是颜色代码，然后分配该颜色代码到前景。就是这样
如果Binded文本值是Color代码，则此操作将更改TextblockForeground的Color，否则default color将更改为shown。

<TextBlock Text="{Binding Text}" Foreground="{Binding Text, RelativeSource=
 {RelativeSource Self}}"/>

或

<TextBlock Text="#0FFFFF" Foreground="{Binding Text, RelativeSource=
{RelativeSource Self}}"/>