Yeah the coloring is just branding, almost all pure compounds are white powders, including fentanyl and analogues. The color is added on purpose to differentiate it, I suppose, and make it recognizable as a particular "type".
Also to whoever said it's obviously heavily cut, well yes, all street fent is heavily cut, otherwise people would be dying in much higher numbers than they already are. A dose of fentanyl is like 1mg or less, which is an extremely tiny amount of powder. A few of the fentanyl analogues (like carfentanyl) are even much more potent than that - carfentanyl is dosed at like 5 micrograms, which is such a small amount of powder it can't be seen with the naked eye. Obviously when people get a big tolerance that dose goes up, but people are used to doing larger amounts of powder and most people don't have scales, so it has to be made into an amount of powder that is similar to what people would be doing with heroin or other drugs they're used to. The reason fentanyl in drugs is so dangerous is because if it isn't cut properly, you have a drug that people will OD on extremely easily. Either it gets cut too little, so it's way stronger by weight than it was expected to be, or, more commonly, it is not cut well, so there are "hot spots" where some of it is much more potent than other parts. Simply fentanyl into an inert powder and mixing it by hand will produce hot spots, proper cutting is a more involved process, if you want to make sure it is evenly distributed. These hot spots in drugs that are not cut properly are responsible for a lot of the deaths. You could be using from the same bag and one time you happen to get a hot spot and that's the time you die.
