Changing the visio shape fill color by axDrawingControl

Hello,

I need to change background and line color of shape in the visio page.

I try by this code->

shape.get_CellsSRC(
(short)IVisio.VisSectionIndices.visSectionObject,
(short)IVisio.VisRowIndices.visRowFill,
(short)IVisio.VisCellIndices.visFillForegnd)
.FormulaU = "rgb(255,0,0)";

with this it's work, BUT the image is not updated... when i go on
"right-click->format->filling" the color of the FillForegnd is RED

how i can refresh the page?

thanks,

Esty