Some block features are rendered with invisible ink with dark backgrounds.

[bph]

This is just an example for the Columns block:

In this video you see me trying to drag and drop a paragraph into a columns block that's above the paragraph, with two 50/50 columns.

When I start dragging the paragraph to a column, I hardly can see 'where I am going'. Although there is a light outline of the paragraph at the beginning, the column block doesn't have a light outline and the blue on black is barely invisible.
Also, the blue landing zone color is barely visible on this dark background.

In the example I use Twenty-Twenty-one.

Steps to reproduce the behavior:

1. Use a dark default color - I used #303030
2. Create a columns block with two columns
3. Create a paragraph block
4. Drag & drop the paragraph block into one of the columns.

Expected behavior
I would expect the block outlines to switch to a light color on dark background.

Screenshots
https://recordit.co/rwoBomnXTU

Editor version:
WordPress version: trunk (5.6. beta someting]
Gutenberg zip from Master 10/23/20]

Desktop (please complete the following information):

• OS: OSX 10.14.6
• Browser Google Chrome
• Version 86.0.4240.80

I first filed this with TT1 repo, but it seems to be an editor bug. I also tested it with the Twenty-Twenty theme and saw the same problem.

There are related issue on this repo (as @carolinan found)

• Add a dark mode to the post title #25796 (fixed)
• Consider revising default quote and pullquote colors in dark mode.  #16732

[bph]

Looking at other core blocks....

Verse
I selected the verse block but did not see what I was typing. Once I highlighted it, I saw there is some text in the editor.
https://recordit.co/CZTnaCTuoh

Gallery
In general, it works, except for the Caption placeholder

Table block
https://recordit.co/HEgrgPiBsp