When Sam's get a file the operator usually does some correction before printing and as you say there is a B/W setting for
grayscale images. However, the best way is to give them a RGB image that is desaturated. When you are satisfied with your image convert it to a profile for the Fuji Frontier. The Pop Photo magazine web site had this profile and instructions for download.
http://www.popphoto.com
If these are no longer available I can post this info.
There are many free professionally made Frontier profiles available at http://www.drycreekphoto.com. See if your machine is there -- many WalMarts, Costcos, Sam's and camera stores are there. Dry Creek has instructions about how to use the profiles, based on Photoshop.
-- jonathan wills _______ wills design portland, oregon, usa