how to apply border color for ion-card using ngClass

i an array like below

this.defaultBackground=[{"applyBackground":"true"},{"applyBackground":"false"}];

in my html i have used ion-card

<div *ngFor="let details of addressArray; let idx = index" 
    [ngClass]="defaultBackground[idx].applyBackground ? 'zerocard':'oneCardData' ">
   <ion-card></ion-card>
</div>

here is my css code

.zerocard{
        .card-ios {
            margin: 12px 12px 12px 0px;
            border: 1px solid $green-color !important;
        }

        .card-md {
            margin: 12px 12px 12px 0px;
            border: 1px solid $green-color !important;
        }

                ion-col[width-80]{
            padding-left: 15px;
            font-family: $font-roboto;
            font-weight: bold;
            color: gray;
        }
        ion-col[width-20]{
            ion-icon{
                color:gray;
                padding-left: 15px;
            }
        }

        ion-card{
            width: 100%;
        }

        ion-card-header{
            padding: 0px;
        }

        ion-card-content{
            ion-row p {
                color:black;
                margin-bottom: -5px;
            }
            ion-row{

                ion-col{
                    margin-bottom: -14px;
                    margin-left: -5px;
                    margin-top: -5px;
                }
                ion-col[width-80]{
                    text-align: left;
                    padding-left: 0px;
                }
                ion-col[width-20]{
                    text-align: right;
                }
            }   
        }
    }

    .oneCardData{
        .card-ios {
            margin: 12px 12px 12px 0px;
            //border: 1px solid $green-color !important;
        }

        .card-md {
            margin: 12px 12px 12px 0px;
            //border: 1px solid $green-color!important;
        }

        ion-col[width-80]{
            padding-left: 15px;
            font-family: $font-roboto;
            font-weight: bold;
            color: gray;
        }
        ion-col[width-20]{
            ion-icon{
                color:gray;
                padding-left: 15px;
            }
        }

        ion-card{
            width: 100%;
        }

        ion-card-header{
            padding: 0px;
        }

        ion-card-content{
            ion-row p {
                color:black;
                margin-bottom: -5px;
            }
            ion-row{

                ion-col{
                    margin-bottom: -14px;
                    margin-left: -5px;
                    margin-top: -5px;
                }
                ion-col[width-80]{
                    text-align: left;
                    padding-left: 0px;
                }
                ion-col[width-20]{
                    text-align: right;
                }
            }   
        }

    }

i have two object from my array which is displayed in my ui in that card i have use two color based upon the 'defaultBackground' array.

the above code always applying only oneCardData css class.

So in my inspect element i am seeing only oneCardData css but my zerocard css is not applyed

update

updated my html part with indext of idx in to get display true or false.

Remove the quotes around the boolean values

this.defaultBackground=[{"applyBackground": true},{"applyBackground": false}];