<i class="el-icon-success" v-if="!scope.row.cat_deleted" style="color:lightgreen;"></i>

<i class="el-icon-success" :style="{color:iconColor}" @click="onColorChange" />
data: {
     iconColor: 'red',
}
methods: {
    onColorChange() {
      this.iconColor = 'green'
    },
}