Why necessarily though? They can just add coloring with the binder when they press it, right? I've never consumed MDMA (yet) but for stuff like the pink Tiktok pills I see at my school, it could be just MDMA but with pink coloring, correct?
Well - high quality tablets can usually be identified because they are pure white usually with a slight twinkle of crystals. But they also use custom dies with a clean and clear logo on the obverse and a break line on the reverse. They are generally bevelled as well and the very best have a shellac coating.
So a badly made pill using an off-the-shelf die that aren't white and aren't even one colour but speckled and lack bevelling, break line and shellac is a good sign that the pill is BADLY made.
It costs money to add a dye and when combined with a speckled finish, it suggests that they added dye to the binder, not to the entire mix going into the press. Adding a dye also messes up presumptive tests. If you have good product, why would you seek to undermine a test that would SHOW that it was a good product? Coloured pills really began to arrive as testing became available.
It doesn't preclude the product from being good, but if you go back to the 80s and early 90s their were Doves, Callies and Sunrises. All of them showed the signs of high quality production. All were white. I admit they cost a lot more but they did always have 120-130mg of MDMA in them so their was some kind of a standard.
But I guess one could add green dye to milk. It would still be perfectly good milk, but it would hardly inspire confidence.
As prices dropped and more organised crime got involved, we saw a lot of very dubious things. One was the action of taking good pills, crushing them down and making more low quality pills. Since people weren't aware of what speckling could mean, adding a colour to prevent this wasn't effective. Then MDEA, MDA and even worse things like 4MTA (seen in Flatliners) turned up. The makers or rather the wholesalers no longer cared about the end user.
I THINK that is why MDMA powder became popular - and I've NEVER seen that coloured. It's chunky crystals that would be hard to fake and of course, it's ideal to test with EZtest or whatever.