Some would have to get doctors' excuses to return. Some would have to go to work blue and take the risk of being fired for drug use. The evidence would be as clear as blue and white. If the next drug use made the blues last eight days, more than one week's vacation would have to be used to stay away from work until the blues disappeared. Not a fun way to spend a vacation.
Most people only get finite numbers of vacation days per year.
Blue would go a long, long way into winning the war against drugs. The biotechnology industry could use the boost in business and we could beat the drug problem. Well a simple marketing campaign may be just as good as the real thing. Simply have the government start a marketing program that educates the public that using drugs may, now, turn you blue. We may even paint up a few actors to display and make the casual drug users uncertain of reality.