Holly,
I just read your post regarding color and would like to add something on the subject that I know and might be helpful for others.
Most of the postcards being discussed here are from one supplier on the west coast. That supplier is an offset printer. They work in CMYK (cyan, magenta, yellow and key or black). When designing your postcard you should use CMYK "process" colors. That means colors that can be achieved by mixing CMYK. You should never use spot color or a pantone color as this would then have to be converted and CMYK can't match all pantone colors. If you do use a spot color the printer will have to lay down an additional color, raising the cost to you or try to match as close as possible.
Also, a match print is always a necessary tool if you are critical regarding the color. With that the printer has a goal that is achievable.
