Since you are talking Glulx, under the covers Parchment is running Quixe. I put together this demo regarding background colors in a previous discussion: eblong.com/zarf/glulx/quixe/quix … Play+it%21 discussion was here: Flexible Windows example with Figures on latest V15 update - #8 by allensocket
Given some of the bugs and incomplete work, it does matter if you use just a single window or additional ones.