Unable to customize UI

[DCost]

I’m followind this guide to customize components styles( such as color, background ) https://github.com/OnsenUI/OnsenUI/tree/master/css-components
After i complete steps in the guide i build my application with “ng build”, then run with cordova on device or serve on browser, i can’t see differences with standard onsen interface.
Any tips? How can i make it work properly?