Thank you for the kind words. I try to not change backgrounds or aspects of her or anything else that isn't relevant to the "plot" when I write dialogues, since I want people to be able to select those aspects as they best see fit themselves. Some might prefer a bedroom setting, some might prefer a hotel trip setting, some might even prefer to be doing this activity at the edge of an active volcano, and I don't want to get in the way of any of those people.
As for the text box color, it might be that the default colors for dialogdisplayedit are too transparent, making them hard to read against certain backgrounds. Try opening the settings file and set the "bgalpha" value to something greater than 1, or feel free to simply use the same one I use.
edit: removed attachment, added a download link in OP as SkyHeart suggested.