In reply to Ducky.

Hi Ducky,
Yes, you can change the background color. You just need to add background-color:your_color; attribute within the textarea style string. For example:
data:text/html,
your_color can be either color name (see https://en.wikipedia.org/wiki/Web_colors) or hexadecimal triplet (some browsers will allow # in front of it, e.g #33aa88, some won't).