如何设置带有全屏裁剪显示情绪的底栏颜色

body {
  background: linear-gradient(to bottom, #ff0000, #0000ff);
}

var now = new Date();
var hour = now.getHours();

if (hour < 12) {
  document.body.style.background = "yellow";
} else if (hour < 18) {
  document.body.style.background = "orange";
} else {
  document.body.style.background = "purple";
}

const express = require('express');
const app = express();

app.use(express.static('public'));

app.get('/color', (req, res) => {
  res.send('<style>body { background-color: #ff00ff; }</style>');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});