I wanted to change the colors of some columns in a table in a DITA topic file, so I followed the directions here to make a CSS file:topic16194.html. I then associated the CSS file with that DITA file.
The formatting appeared in Oxygen:

But when I generated a PDF, the formatting didn't appear. The table just looked like all the other tables in the DITA map. The table in the PDF looks like this:

Something in the transformation from DITA map is making the CSS formatting not be applied. How can I get the generated PDF table to have the colors?
Thank you