Ionic Ion-checkbox change color in typescrypt

I want to change the color of the ion-checkbox in the typescript

  <ion-item >
    <ion-label id="check1">No</ion-label>
    <ion-checkbox color="blue"  id="box1" [(ngModel)]="todo.check1"  name="check1"></ion-checkbox>
  </ion-item>

I try this:

document.getElementById("box1").color = "dark";

but it doesn't work

I also try to change the class: doesn't work

Thanks for you help