Set post CSS style from Post Submission form

I have created a GravityForm that lets users submit posts from the front end and defines the category that will be assigned to the post. I am trying to have the form set the final post's custom CSS style by using a Custom Field, but it's not working.

The post submission form is at http://www.fsa-cc.org/womencare-editor/. Once you submit a post, it will appear in the sidebar of the parent page for the category (http://www.fsa-cc.org/womencare/). If you click on the post title in the sidebar, you'll go to the full post page (http://www.fsa-cc.org/womencare/, followed by whatever you entered as the Title on the Gravity Form). For this category, the background should be a brick-red pattern (the same background that appears on http://www.fsa-cc.org/womencare/). Instead it is displaying the teal background that is the site default.

This section of the site (everything that has "womencare" in the URL) is not live, so you can try submitting a post for testing purposes. The form will be password protected once it goes live.

Each post category has a custom body class which uses category-specific styling to set the background color, etc.. Our Gravity Form uses a custom field to set the category. The custom field on DOES set the post to the correct category and correctly displays the post only on the sidebar assigned to that category. It does NOT carry on to set the custom body class.

FYI, the site is built on Thesis, if that matters to choosing the correct custom field.

I have temporarily removed the password so that you can experiment. I will have to put the password back by the end of the week.