Two articles, same flick of the toggle. The design talk only gets you so far. It's easier to just see it.

A BBC news article green page tint
Before
A BBC news article in its default state, before Lexa is on
After · Lexa on
The same BBC article with Lexa on, showing a soft green page tint and wider letter spacing

A soft green wash over the page, the font swapped to Atkinson Hyperlegible, more space between letters, and numbers picked out with a yellow highlight.

A Wikipedia article on Japan rose page tint
Before
A Wikipedia article on Japan in its default state
After · Lexa on
The same Wikipedia article with Lexa on, showing a rose page tint

Same page, different mood. Rose tint this time, and the numbers in the article get the same highlight so they don't disappear into the prose.