Ionic 4 button ngStyle background-color

Ionic Framework
10

Here is my scenario:

I have a number of buttons and each should be colored depending on if they were selected.
I used [ngStyle] to color them based on a var withing the buttons parent item in a list.
I actually had these in slides to boot.
So, the var that determines if they are a different color is: cat.isSelected

<ion-slides>
            <ion-slide class="catSlide" *ngFor="let cat of categories_ar; let i = index">
                <ion-buttons slot="start">
                    <ion-button class="catBtn" ion-button small (click)="select_category(cat)" [ngStyle]="!cat.isSelected&&{'background-color':'green'}||{'background-color':'pink'}">{{cat.title}}</ion-button>
                </ion-buttons>
            </ion-slide>
        </ion-slides>

with ngStyle I cannot set the color.
With style, I can set the color but not use condition

Avoiding these two options and doing it in scss, how would I pass each individual cat.isSelected to the condition?

.catBtn{
@if (isSelected) {
–ion-color-base: yellow!important;
}
}