How to change color of visio timeline object through excel

This is what I am trying to do with timeline object and excel.

1. Create a timeline - DONE

2. Add timeline objects - various shapes and color - DONE

3. Export object data to excel - DONE

4. Import the same data and link with timeline objects - DONE

5. Use excel to change timeline object color - NOT Working

This last step is not working at all, I am using the field "FillForegnd" and updating it using RGB(255,0,0) etc. but on refreshing the data in visio, the object color is not changing.