Trouble animating a SolidColorBrush

I have the following code:

<Grid.Background>
                <DrawingBrush Stretch="Uniform">
                    <DrawingBrush.Drawing>
                        <DrawingGroup>
                            <GeometryDrawing Brush="{Binding Path=Segm开发者_如何学PythonentBackground, ElementName=Segment, Mode=OneWay}" x:Name="SegmentDrawing" Geometry="M 278.229,141.688C 278.229,128.798 276.451,116.324 273.128,104.497L 228.906,122.309C 230.417,128.8 231.216,135.565 231.216,142.517C 231.216,147.98 230.723,153.328 229.778,158.518L 275.262,170.2C 277.206,161.002 278.229,151.464 278.229,141.688 Z ">
                                <GeometryDrawing.Pen>
                                    <Pen LineJoin="Round" Brush="#FF000000"/>
                                </GeometryDrawing.Pen>
                            </GeometryDrawing>
                        </DrawingGroup>
                    </DrawingBrush.Drawing>
                </DrawingBrush>
            </Grid.Background>

My question is simple, I want to animate the Brush property of the GeometryDrawingBrush. The drawing is the main visual of my control, and I want the color of the brush to change to reflect it's state (Normal,Over, etc.).