Typically; four-color, white field inlays are all the same shade of white (discounting fade cases) except for when a process in the printing where at start the white coated stock can be various shades of beige resembling nicotine discoloring... There is a thread archived pertaining to early Resorts AC inlays where someone who was in the printing business explains what took place in that process... and, of course, those various shades of beige are only on one side -- and would be very unusual to see that portion of the stock on both sides though, there are some known (confirmed). A lot has changed in the offset printing process since I left Globe Albums (record album jackets) in 1972, to know if that's still possible today...