WPf 中，怎么为GRID的单元格设定不同的背景色

<Grid>   <Grid.RowDefinitions>          <RowDefinition Height="0.5*" />          <RowDefinition Height="0.5*" />   </Grid.RowDefinitions>  <Grid.ColumnDefinitions>         <ColumnDefiniton Width="0.5*"/>         <ColumnDefiniton Width="0.5*"/>  </Grid.ColumnDefinitions>  ＜Label Grid.Column="0" Grid.Row="0" Background="SpringGreen" ＞＜/Label＞  ＜Label Grid.Column="0" Grid.Row="1" Background="RoyalBlue" ＞＜/Label＞  ＜Label Grid.Column="1" Grid.Row="0" Background="Violet" ＞＜/Label＞  ＜Label Grid.Column="1" Grid.Row="1" Background="Red" ＞＜/Label＞</Grid>