Very clever. I hadn't used "Fill" options before, so another thing learned. Just for fun, I tried to extend your example to include a black line dividing the two regions (I made the regions Red and Green, Shmoo colors). Couldn't see the line until I thought to myself, "Which plot is on top?". While I don't "know" the answer, experimentation showed that plotting the line as Plot 0 made it nicely visible. It would be (much) more work, but one could also "draw" grids using similar techniques.
I had a situation where I needed to plot trial outcomes (it was a behavioral test -- if they got it right, the next time you turned the volume down, and if they got it wrong, you turned the volume up). I plotted "volume" as points, and wanted to code "Success" as Green Points and "Failure" as Red Points. My plot was a Chart, so I could see the trials evolve, adding the new (red or green) point each trial. Oops, all the points on a plot need to be the same color. Solution -- make two plots -- Success in Green, Failure in Red. If the outcome was Success, plot Volume on the Success channel, and plot NaN on Failure (NaN, conveniently, fails to plot!). For Failure, do just the opposite.
Plotting appears to be limited in LabVIEW, but clever tweaking can produce some amazing results!