Plain text to rtf and background color

I normally use a template that produces an rtf document with background color (because the white is hard on my eyes). But I’ve just imported many plain text files and would like to find a quick way to turn these into rtf files with background color. I know that I can use Format>Make Rich Text and then use the Fonts dialogue box (Cmd-T) to set the background color.
Is it possible to create script/s to perform these functions on many files at once?

It’s possible to change the background color of all plain text files by opening the Colors panel (while a plain text has the focus), enabling the “Background” checkbox and choosing the desired color.