From 1995/1996? model years and onward, GM specified Dex-Cool in their vehicles (read Prism). Was this way with the Pontiac Vibes vs Toyota Matrix as well.
Now to read between the lines - Saturn Vue has a Honda engine, GM recommends Dex-Cool, but the same engine in the Honda vehicle recommends NOT using Dexcool.
If it is of any worth, the "factory" fill is Toyota Red, if serviced since then by a shop, it will likely have Dex-Cool. Easiest way to find out is to look at the color. Toyota coolant is red, Dex-Cool is more orange in color.
If in doubt, flush all the old coolant with plain distilled water, until drain water runs clear and fill with your coolant of choice.
Fish, I don't normally disagree with you but I have to point out that the owner's manual on my 2001 Prizm does not specify Dexcool. It just says use any antifreeze in which ethylene glycol is the primary ingredient.
Nevertheless I do believe the factory fill on mine was red in color.
Be careful of mixing coolants. my car used orange dexcool and i ran green in there it said 'universal' however the green that I ran through has been found to turn to jelly when mixed with orange decool. Luckily I haven't had this issue.... yet