Nuxt/examples/with-tape/pages/index.vue

<template>
  <div>
    <h1 :class="className">Hello {{ name }}!</h1>
    <button @click="changeColor()"> Change h1 Color </button>
  </div>
</template>

<script>
  export default {
  	data() {
  		return { name: 'world', className: 'red' }
  	},
  	methods: {
  		changeColor() {
  			this.className = this.className === 'red' ? 'blue' : 'green'
  		}
  	}
  }
</script>

<style>
  .red {
  	color: red;
  }
  .blue {
  	color: blue;
  }
  .green {
  	color: green;
  }
</style>