Styling button in ionic2 conference app?



I’m in need of understanding styling mechanism of button in ionic2 conference app, page schedule.html

 <button ion-item (click)="goToSessionDetail(session)">
    {{session.timeStart}} &mdash;

See below image, the color icon on the left of button. Please explain me on this magic, thanks!

Repo Url of this app:


Check out your style variables in the www\build\main.css folder:

These are the class delimiters:

page-schedule ion-item-sliding[track=ionic] ion-label


I got this, it works, thank you.