It depends on the cause.
It could be surface soil in the finish, actual tile wear, plasticizer migration from mats, asphalt track-in, or some other cause.
You may be able to remove or considerably lighten the discoloration by stripping the floor and reapplying several coats of floor finish.
Test strip and recoat by hand a 3- or 4-inch square area to determine product, process, and results before you ...
— Bill Griffin, www.cleaningconsultants.com