WPF中textBlock 变色功能

       
  <window.resources>
 <storyboard x:key="onloaded" repeatbehavior="forever" autoreverse="true"  >
            <coloranimationusingkeyframes storyboard.targetproperty="(foreground).(solidcolorbrush.color)" storyboard.targetname="btn_register">
                <easingcolorkeyframe keytime="0:0:1" value="lightblue"/>
                <easingcolorkeyframe keytime="0:0:2" value="lightgreen"/>
            </coloranimationusingkeyframes>
        </storyboard>
    </window.resources>
    <window.triggers>
        <eventtrigger routedevent="frameworkelement.loaded">
            <beginstoryboard  storyboard="{staticresource onloaded}"/>
        </eventtrigger>
    </window.triggers>

<button
                    name="btn_register"
                    margin="62,26,-60,2"
                    content="新用户注册"
                    command="{binding path=registercmd}"
foreground="#ff91b9ea" grid.column="2" width="auto" fontweight="bold" fontsize="14"/>