In older versions of Confluence, you could clearly distinguish between normal text and Info or Warning macro.

In newer versions the difference is nearly invisible. Something like this (did you notice that the i is in another color?).
I really have to turn my head to some queer angle to see the diff. Too bad !!!!
This is also true for the compare page (compare historic versions of a page).

Probably a visible border would do much (a slightly darker border very much improves the contrast perception, even if the fill colour stays the same).