Change “empty” rectangle box colour/opacity?

Just left a 5 star review – this is perfect!

Was wondering if this is something that bugs you/a feature you might want to add:

In Gutenberg (for some unfathomable UI choice) empty containers have a black outline, with that ” + ” in middle (hover: “add block”).
Why on earth are they black? Not dashed, low opacity, or only on hover!?
I cannot fathom the reasoning of this UI – it’s terrible, bad, no good! ??

Anyway – any interest in adding options to control these – as per the other containers? Would be best to distinguish from containers with seperate options, but they could be exactly the same options and it’d work dandy!

Myself, I’m gonna do something like the below till then ?? :

.block-editor-button-block-appender {
    inset 0 0 0 0.025em #4fff0f9c;
}