How can I customize the style of a foreign component without using the now-deprecated ::ng-deep?

Question

In my app, I am using a component that comes from ngx-bootstrap.

I want to customize the look of the component (in this case, tabs), by making the tabs themselves appear green. Previously I could use /deep/ in my SCSS, to target all selectors used within my component. But I do not want to use something that is deprecated. So how can I get my code below, to turn the a tags within the ngx-bootstrap Tabs, yellow ?

import { Component } from '@angular/core';

@Component({
  selector: 'h3-my-component',
  template: `
    <h1>This is my COMPONENT</h1>
    <tabset>
    <tab heading="Tab 1" id="tab1">content</tab>
    <tab heading="Tab 2" id="tab2">content</tab>
  </tabset>`,
  styles: ['tab a { background-color: green }']

})
export class DemoTabsBasicComponent {}