The base should be white or you will not be able to achieve white in your prints, and whites in the print is a good way of checking your color filtration settings.
I have gotten old color paper in enlarger deals and had to get rid of it all of and use fresh paper (Fuji Crystal Archive Type II). No problems with this paper and I store it in the refrigerator, placing the box in a plastic bag, when it will not be used for a while.
I once tried the Ultrafine house brand, probably the same as other suppliers carry, and it was nowhere near as good as the Fuji paper. Unique Photo has good prices on the 8x10 and 11x14 Fuji paper.