When you define two themes, one light and one dark. It shows a button for switching light and dark, which is very good. 

However, if you choose the dark mode and switch between different pages, chapters or sections. The website is flashing to the light mode first and change to dark theme. It is obvious and easily noticed. 

I don't know the reason, but Hugo website do not have this issue. Quarto is great and I really like it, hope it better. Thanks. 
2022-05-26T23:34:05Z
wenyaoliu
early-in-release
v1.4
open
Flashing when switching between pages in dark theme. 
https://github.com/quarto-dev/quarto-cli/issues/1325