As said before, its not really strange, its just that there are a lot of things which turn orangeish with Marquis.. Harmine also turns orangeish, so if you had some harmine, which is totally legal, they would think its meth (or amphetamine, that also turns orange). So you see how using just one reagent doesnt tell you much abut a substance.. If you use several different reagents, like marquis, mecke, mandellin, ehrlich, etc, then you can see all the color changes (or no reaction) and have a better idea of the substance. But the police dont care about that, they do a first test just to see if it might be illegal, and later on they might send to a real lab that will probably test with gas-chromatography, and then there will be very little room for mistakes.