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. 
I’ll tell the full story below. But before I do , if there is at least one doctor reading this I want to ask for him or her and for everyone reading this to do something to make a change in the system so people wouldn’t be treated for a symptom at any point but tested for the cause and informed about prevention!
Let’s join PPI groups, hospital committed, patient comities and write letters to policy makers. Because while everybody’s different and some deseases are hard to diagnose most of the times they’re missed due to just treating the symptom or trying to convince the person they’re not ill!!!