Restore White Mud Flap Lettering

Restoring white lettering on mud flaps, plastics or tires, is simply a matter of having the right tool for the job. These Tire markers are designed to add the white lettering to tires.

https://www.amazon.com/Trimbrite-T1925-White-Tire-Pencil/dp/B00029XC2M/ref=sr_1_fkmr0_2?keywords=Sharpline+Trimbrite+Tire+Markers&qid=1560643448&s=gateway&sr=8-2-fkmr0

Less permanent option but is available in different colors:

https://www.amazon.com/Tire-Ink-Permanent-Waterproof-Available/dp/B071DT5CF4