It can not Grayscale mode.
Not found Grayscale button.
No color design.
サイトごとにグレースケール表示をかんたんに切り替えできると思いましたが、そうではありませんでした。
グレースケールボタンはどこにもない。
このアドオンの画面は色彩設計がされていません。目が痛い。

Great Extension! One thing i would wish is a more structured font-management.

it feels pretty chaotic insering all fonts in just one line.
Maybe also integrate custom categories for the fonts.

I never write reviews. But this extension is gold. I created account just to say thank you.

Update: My firefox was broken. The extension works fine.

Ankit Ahuja has done a great job of improving this extension. I'm spoiled. Sometimes in other applications, I (mistakenly) want to change the interface, as if I were here in Firefox. Before the author fostered the extension, I was stuck in Chrome because that's where Stylebot was. Now it works in Edge too. Maybe a steep learning curve, and it's pretty deep, it's a techie thing for sure, but it's productive and very rewarding. BTW... Developer Tools (F12) can be helpful for using Stylebot (I mean using, not learning).