It's the one below the one ashwinsundar linked, "detection of artificial colour in turmeric powder".

The test is: when you add the powdered turmeric to water, natural turmeric will give the water a "light" yellow color, while adulterated turmeric will give it a "strong" yellow color.

This is not a test that I'd characterize as "easy" or "reliable".

Yeah, I wouldn't trust this test without a reference sample for comparison.

It's used for coloring, because it makes it apparently gives it the same color as good real tumeric

OK, so the method given for artificial coloring on that page. I'm curious if that works for lead chromate. It seems so simple that it must have been tried in this case? Regardless I'll file it away to at least try on stuff to avoid what colors it can detect.