I know this is an old discussion, but someone stumbling on to it might want to know of the following way to set the platform heading text color, although it is not a preference, so it won't affect all reports.
In JMP 15, possibly earlier, right click on the gray triangle (disclosure icon) and choose Edit >Show Properties.
You'll get a Properties panel on the right side that has a Text Color control. Click on it to choose a color.
You can click on parts of the report and set the Text Color or other properties differently than the platform heading.
When you're done, close the Properties panel by clicking on the x to the right of the word "Properties".
It it doesn't help you @MichaelCallahan, I hope it will at least help someone else dropping by this discussion.
~John