The ability to modify CodeMirror colors

[n-splv]

Problem

After upgrading from 3.6.4 to 4.0.9 I found some unpleasant visual changes, that made me rollback.
For instance, the square and curly braces are too faded, the spaces between lines are too large, f-strings are purple and so on.

I tried to apply the previous style to the new version by copying the contents of my-conda-env/share/jupyter/lab/themes/@jupyterlab directory from the old environment with Jupyterlab v3.6.4 to the new one as proposed here, but it didn't help.

Proposed Solution

AFAIK it's not Jupyter's decision to alter the code editor colors: you've just adopted a newer version of CodeMirror. While it might be beneficial to make the brackets less annoying noticeable in languages like JS, this is not the case for Python, which is the most popular language in Jupyter. It would be great if you gave this a second thought.

Meanwhile, please help me understand whether it's possible to manually revert to the old editor style on the new version. Thanks!

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[JasonWeill]

@nick-maykr Thank you for opening this issue! In JupyterLab 4, we upgraded CodeMirror from major version 5 to 6. This change affected a lot of CodeMirror's functionality and organization, and required JupyterLab to make changes to accommodate the upgrade. You can see more details on CodeMirror's migration guide. I'm not sure whether you can use CodeMirror 5's style in CodeMirror 6; what is more likely is creating a new CodeMirror 6 style that looks like version 5. This may be a good use case for a new extension or theme.

[krassowski]

@n-splv you may like the new jupyterlab-rainbow-brackets extension; I know that from the name it sounds opposite to what you are trying to achieve but hear me out: your rainbow can be all black because it is fully customizable.