Changing the css class of Button on Alert

Hi I'm really struggling to change the color of the buttons in a alert. I don't want to change the default since the alert shoud have three different color buttons. For starters I just want to change one button's color to red.

.ts file:
`let alert = this.alertCtrl.create({

  title : title,
  message : text,
  inputs: [
    {
      name: 'pin',
      placeholder: 'Pin'

    }
  ],
  buttons: [{
    cssClass: 'buttoncss',
    text: 'btnType',
  }]
});

alert.present();`

.scss file:

`let alert = this.alertCtrl.create({

  title : title,
  message : text,
  inputs: [
    {
      name: 'pin',
      placeholder: 'Pin'

    }
  ],
  buttons: [{
    cssClass: 'buttoncss',
    text: 'btnType',
  }]
});

alert.present();`

Thanks