初めてNode-REDを使ってみよう、というかたのためのガイドです。
Node-REDを使ってシンプルなウェブサイトを作ってみます。

1. シンプルなhtml出力

Node-RED - フローをコピーする方法を参照し、下記のフローをコピペします。

シンプルなhtml出力

[{"id":"95140036.80b9b","type":"http in","z":"75eef29b.360a7c","name":"","url":"/test10","method":"get","swaggerDoc":"","x":130,"y":100,"wires":[["22e702b3.031ca6"]]},{"id":"22e702b3.031ca6","type":"template","z":"75eef29b.360a7c","name":"hello","field":"payload","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"<html>\n    <body>\n        Hello.\n    </body>\n</html>","x":330,"y":100,"wires":[["dca7bf27.e28b7"]]},{"id":"dca7bf27.e28b7","type":"http response","z":"75eef29b.360a7c","name":"","x":510,"y":100,"wires":[]},{"id":"aa7e19fb.5c109","type":"comment","z":"75eef29b.360a7c","name":"シンプルなhtml出力","info":"","x":150,"y":60,"wires":[]}]

ブラウザでlocalhost:1880/test10へアクセスし画面を確認し、"Hello"と表示されるのを確認します。
Node-REDでhelloと書かれたテンプレートノード（オレンジ色）を開き、ｈｔｍｌの内容を確認します。

test10.html

<html>
    <body>
        Hello.
    </body>
</html>

2. 色を付けてみます

Node-RED - フローをコピーする方法を参照し、下記のフローをコピペします。

色を付けてみました

[{"id":"fccc0188.38ce6","type":"template","z":"75eef29b.360a7c","name":"test12.html","field":"payload","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"<html>\n    <head>\n        <style type=\"text/css\">\n            {{{payload.css}}}\n        </style>\n    </head>\n    <body>\n        <div id='a1'>\n            こんにちは\n        </div>\n    </body>\n</html>","x":470,"y":240,"wires":[["aaa886bb.30565"]]},{"id":"315eb68c.aab76a","type":"template","z":"75eef29b.360a7c","name":"css","field":"payload.css","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"#a1 {\n  background-color:  #98d98e;\n  padding: 20px;\n  height: 100px;\n}\n","x":310,"y":240,"wires":[["fccc0188.38ce6"]]},{"id":"41bc502c.15aed","type":"http in","z":"75eef29b.360a7c","name":"","url":"/test12","method":"get","swaggerDoc":"","x":130,"y":240,"wires":[["315eb68c.aab76a"]]},{"id":"aaa886bb.30565","type":"http response","z":"75eef29b.360a7c","name":"","x":630,"y":240,"wires":[]},{"id":"51cb04f7.19a094","type":"comment","z":"75eef29b.360a7c","name":"色を付けてみました","info":"","x":150,"y":200,"wires":[]}]

ブラウザでlocalhost:1880/test12へアクセスし画面を確認し、緑地に「こんにちは」と表示されるのを確認します。

Node-REDでcssと書かれたテンプレートノード（オレンジ色）をダブルクリックして開き、スタイルシートの内容を確認します。

test14.css

#a1 {
  background-color:  #98d98e;
  padding: 20px;
  height: 100px;
}

Node-REDでtest12.htmlと書かれたテンプレートノード（オレンジ色）を開き、ｈｔｍｌの内容を確認します。

test14.html

<html>
    <head>
        <style type="text/css">
            {{{payload.css}}}
        </style>
    </head>
    <body>
        <div id='a1'>
            こんにちは
        </div>
    </body>
</html>