Color conversion within a PDF is done using the Pre=flight tools, only available in the Professional variation of Acrobat.
You my need to write your own color conversion pre-flight droplet and call that from within your Action.
There is a pre-flight droplet to convert to gray scale but is it locked so I cannot tell if it will meet your requirement.
Thanks GKaiseril, but a preflight droplet isn't quite what I'm looking for. Droplets need installed as part of each stations installation. I'm looking at 40+ computers. The rest of the script just runs "under the hood" of the programs. I'm working with the pro versions of Acrobat, currently v11.x (although we have DC as well)
The install for Acrobat can be customized to add JS script files tot the application folders so there is no need for a user to add the scripts manually. The scripts would be added upon install or when your IT function applies updates to Acrobat.
Note all users must be using Acrobat Professional so one has access to pre-flight.