It’s possible your OP was noticing that a certain smell makes him know a thing is purple. Under normal circumstances he would just perceive PURPLE and think he was seeing. But on drugs he might perceive that his nose was also alerting him of PURPLE in the flower.
So, I've heard that people make a big deal about choosing a mantra, but my thinking was it can be anything, and somehow I got into the habit of visualizing a blank field of a particular color. The nice thing about focusing on a color was that if my visual imagination distracted me, I could concentrate on "seeing" the color, while if I was imagining words or sounds, I could focus on the name of the color too. So it was like having an object to focus on that had all the different angles available.
I'm not sure I've never experienced synaesthesia, but I'm pretty sure I haven't been perceiving smells or sounds as having color recently.
Even though this episode was decades ago, I still, kind of, experience the scent of that flower as the colour purple.