InfoPath table gridline colour issue

I have a InfoPath 2003 form with some tables that have black borders and gridlines when loaded in InfoPath 2003.

We are migrating to InfoPath 2010 and when loaded in 2010 the borders and gridlines for some tables are showing in grey.

I have tried converting the form to 2010 format and then changing the colour to black, but nothing happens when I click ok. I go back into the Borders and Shading box and it is stil grey. The form is very complicated and I don't want to have recreated the affected tables if possible.

Thanks

JT