Ionic back button is invalid

Ionic Framework
1

I’m new to Ionic, I found that back button on the header is invisible when I set the background color, how can I create a back button with colorful background. My code is below.

questions

.title{
background-color: orange;

1613663009(1)
1613663009(1)405×718 1.43 KB

}

2 
<ion-button fill='clear' slot="start">

  <ion-back-button></ion-back-button>

</ion-button>

<ion-title >questions</ion-title>