Different highlight colors

It's nice that there's different highlight colors for the text, but it'd be better if we could choose our own color presets. I only use dark mode and all the highlights are still too bright, imo. I'm forced to use the ‘no highlight’ option but I end up losing my place alot while reading, especially if the screen doesn't auto scroll. It'd be so helpful if I could pick my own dark gray color so I can still see the text box but not kill my eyes while reading at night. If I fiddle with the color code, I can find a color that I like but it won't let me save it, it only allows the 8 preselected colors you chose. I wish I could use the darker color I picked instead. Could this maybe be a feature you add in the future? I have really sensitive eyes so any little bit helps. Thanks.