Ionic 4 : overiding sass variable

Hi everybody!!
I’ve starting to test the new ionc 4… playing into a simple angular 5 cli project. It work find!!

But after searching longtime… i can’t find the way to overide ionic 4 sass variable in a simple angular cli project.
I’ve try to add rule into my root project stylesheet ./src/style.scss but nothing a change…
I’v try with the colors, grid-columns and other but nothing work.

Have you an idea to how change/overide scss variable in ionic 4?