Feature request (or help): Use different colors for posterior draws for some parameters in mcmc_area()  #280

I'd like to the color of a few specific variables in my mcmc_area() plot to be one color, while the rest are another color. Referencing your plot from the Posterior uncertainty intervals vignette, say I wanted only the pars = "cyl" posterior distribution in blue, and the rest ("drat", "am", "sigma"), still in red. Is this already possible and I'm failing to figure it out? Thank you for your beautiful and helpful package!