Ralf does demonstrate it at the end of this "Fractal Terrains to Parchment World" tutorial (around the 38 minute mark), using a full world Parchment Map that he had created the week before.

I highly recommend the tutorials, too. I spent five years thinking I could learn it just from the PDF manuals, which are great references but I couldn't quite get it from them. Joe Sweeney's "Parrot Island" tutorial really made things click for me. From there, I watched more of Joe's tutorials, and then some of the shorter ProFantasy ones. Remy Monsen created a page describing the video tutorials. I'd start with Learning CC3+ and Campaign Cartographer Concepts, and then fill in with the Quickies to learn specific techniques before moving on to the Live Videos.

The Live Videos are fantastic, but some of the more recent ones may be a bit advanced for newcomers until they get the hang of the basic fundamentals. I watched one of the more advanced ones when I was first learning, and it was way over my head -- but really great in showing me the power and potential of CC3+. And now that I've grasped the fundamentals, I'm addicted to the Live shows, though I usually have to watch hours later. For me, they're very peaceful. I love seeing how a blank canvass can evolve into a work of art. I've watched the two Forest Trails ones multiple times when I need a soothing, bucolic break in nature.

We've been thinking of colors for sewers that are used for their traditional use. But if we start to think of the reasons why a necromancer might need a sewer-type system beneath their lair, or a demon lord, or an archfey, or even dwarves creating subterranean aqueduct, then all sorts of colors make sense: bright water, glowing green goo, rivers of blood, lava...the possibilities are endless.