The dark mode has already been developed and is part of a new version release.
It’s expected to be online in about 2 weeks.Lazar Ranisavljevic commented
I sent you a suggestion on the google store for the dark theme a day or so ago. I think that would be an awesome addition. Seeing as my complete internet experience is customized to be dark even the cursor popup of the Power Thesaurus appears dark for me and it does not break the page feel. The toolbar part and the settings page are a different story and I avoid using them since they poke my eyes. I would love to include a screenshot but I do not see an option here, however, here are some colors which work well together:
Mind you, this is basically the same comment I left on the store, only more elaborate, but I just found this suggestion.