Vue

HTML

<div id="app">
  <div v-for="(item,index) in items" :key="index">
     <div :class="{ active: item.active}" @click="toggleActive(index)">
          {{ item.foo }} 
          {{ item.number }}
     </div>
</div>
</div>

CSS

.active {
  color: red;
}

Vue

new Vue({
  el: "#app",
  data: {
    items: [
   {
       foo: 'something',
       number: 60
   },
   {
       foo: 'anything',
       number: 15
   },
   {
       foo: 'text',
       number: 20,
   }
]
  },
  methods: {
  	toggleActive(index) {
        let item = this.items[index];
        
        item.active = !item.active;
        
        this.$set(this.items, index, item);
        
    }
  }
})