Yes. Legal rules vary from state to state where marijuana is now legal for recreational use. Also, as marijuana stays in the system over a prolonged period of time, the employee may use marijuana legally, but be drug tested at a later time and lose their job. In general, according to Law360, marijuana legalization laws in states where it is legal support employers in drug testing for marijuana use and firing people for it. Marijuana use is still illegal under federal law, and many employers prefer to maintain their drug-free workplace policies.
There are five primary color-tests reagents used for general screening purposes. The Marquis reagent turns into a variety of colors when in the presence of different substances. Dille-Koppanyi reagent uses two chemical solutions which turns a violet-blue color in the presence of barbiturates. Duquenois-Levine reagent is a series of chemical solutions that turn to the color of purple when the vegetation of marijuana is added. Van Urk reagent turns blue-purple when in the presence of LSD. Scott Test's chemical solution shows up as a faint blue for cocaine base.