Transparent background (comments)

Hello!

I need all the comments to have transparent background so that the highlighted text is readable in both a normal editor (white background of the page) and a full-screen editor (dark grey). In the “Tools > Options > Appearance” menu, I’m able to set the transparency only for a new comment – whenever I restart the Scrivener, all comments turn white. Now, color of comments can be set via the Inspector, however, the color palette there does not give me a possibility to set the value of the alpha channel to 0.

Am I missing something? Is there any way to set transparent background to all comments, new and old?

Thank you for any suggestions.