Comments background changes color on reopen

I’ve noticed that the background color of my comments are resetting to yellow when I close and reopen the scrivener file.
I think this is happening because in the options menu I’ve set the alpha channel to zero so that the comments background is transparent. But in the color menu for comments when opened from the inspector (right-clicking “More” on the comment), there is no option for an alpha channel, just red, green and blue.
I’ve included screenshots for reference.

Thanks for the catch!