They can do that because most tires have white under them so they can simply remove some black to make white lettered tires or whitewalls, etc. Drive with a flat tire for a while and you will soon have a "whitewall".

 

no they def add something to the tire

 

Not all tires ahve white under them. But all of the cheap narrow white walls and raised white letetr tires do have a full strip of white. You can take a raised white letter tire or narrow white wall and turn them into wide white walls. But sadly, they dont make cheap narrow white walls in 55 series, the lowest profile I find was 70-series. Great for hoopties, btu not for HHRs.