Can you look in the log for errors or notes. I'm guessing that your updated style template is not found on the server where output for the IDP is being created. You should see a note in the log to the effect:
WARNING: Style xxxxxxxx not found; Default style will be used instead.
You might want to work with Tech Support on this issue. Depending on when/how/where your template is being compiled and saved, you may need an ODS PATH statement so that the Stored Process can find the updated template.
Have you tested your style template code in Base SAS (outside a Stored Process to make sure that the code has the desired result)??
DanH ur initial suggestion of " backgroundcolor = white " worked.
I did not see the results as I am using the tagsets.tableeditor template and this that script happpends to create a style tmeplate also called MyStyle. This was replacing my style template.