While not officially supported, this can be done via User Scripts like Violent Monkey browser extension:
- Install the browser extension linked above.
- Create a user script in the extension
- In the script, paste the following:
// ==UserScript==
// @name Code Editor patch - playcanvas.com
// @namespace yaustar
// @match https://playcanvas.com/editor/code/*
// @grant none
// @version 1.0
// @author @yaustar
// @description 15/11/2021, 17:46:17
// ==/UserScript==
(function () {
// Load a chosen theme
var loadTheme = function () {
// Taken from: https://github.com/brijeshb42/monaco-themes/tree/master/themes
var data = {
"base": "vs-dark",
"inherit": true,
"rules": [{
"background": "282a36",
"token": ""
},
{
"foreground": "6272a4",
"token": "comment"
},
{
"foreground": "f1fa8c",
"token": "string"
},
{
"foreground": "bd93f9",
"token": "constant.numeric"
},
{
"foreground": "bd93f9",
"token": "constant.language"
},
{
"foreground": "bd93f9",
"token": "constant.character"
},
{
"foreground": "bd93f9",
"token": "constant.other"
},
{
"foreground": "ffb86c",
"token": "variable.other.readwrite.instance"
},
{
"foreground": "ff79c6",
"token": "constant.character.escaped"
},
{
"foreground": "ff79c6",
"token": "constant.character.escape"
},
{
"foreground": "ff79c6",
"token": "string source"
},
{
"foreground": "ff79c6",
"token": "string source.ruby"
},
{
"foreground": "ff79c6",
"token": "keyword"
},
{
"foreground": "ff79c6",
"token": "storage"
},
{
"foreground": "8be9fd",
"fontStyle": "italic",
"token": "storage.type"
},
{
"foreground": "50fa7b",
"fontStyle": "underline",
"token": "entity.name.class"
},
{
"foreground": "50fa7b",
"fontStyle": "italic underline",
"token": "entity.other.inherited-class"
},
{
"foreground": "50fa7b",
"token": "entity.name.function"
},
{
"foreground": "ffb86c",
"fontStyle": "italic",
"token": "variable.parameter"
},
{
"foreground": "ff79c6",
"token": "entity.name.tag"
},
{
"foreground": "50fa7b",
"token": "entity.other.attribute-name"
},
{
"foreground": "8be9fd",
"token": "support.function"
},
{
"foreground": "6be5fd",
"token": "support.constant"
},
{
"foreground": "66d9ef",
"fontStyle": " italic",
"token": "support.type"
},
{
"foreground": "66d9ef",
"fontStyle": " italic",
"token": "support.class"
},
{
"foreground": "f8f8f0",
"background": "ff79c6",
"token": "invalid"
},
{
"foreground": "f8f8f0",
"background": "bd93f9",
"token": "invalid.deprecated"
},
{
"foreground": "cfcfc2",
"token": "meta.structure.dictionary.json string.quoted.double.json"
},
{
"foreground": "6272a4",
"token": "meta.diff"
},
{
"foreground": "6272a4",
"token": "meta.diff.header"
},
{
"foreground": "ff79c6",
"token": "markup.deleted"
},
{
"foreground": "50fa7b",
"token": "markup.inserted"
},
{
"foreground": "e6db74",
"token": "markup.changed"
},
{
"foreground": "bd93f9",
"token": "constant.numeric.line-number.find-in-files - match"
},
{
"foreground": "e6db74",
"token": "entity.name.filename"
},
{
"foreground": "f83333",
"token": "message.error"
},
{
"foreground": "eeeeee",
"token": "punctuation.definition.string.begin.json - meta.structure.dictionary.value.json"
},
{
"foreground": "eeeeee",
"token": "punctuation.definition.string.end.json - meta.structure.dictionary.value.json"
},
{
"foreground": "8be9fd",
"token": "meta.structure.dictionary.json string.quoted.double.json"
},
{
"foreground": "f1fa8c",
"token": "meta.structure.dictionary.value.json string.quoted.double.json"
},
{
"foreground": "50fa7b",
"token": "meta meta meta meta meta meta meta.structure.dictionary.value string"
},
{
"foreground": "ffb86c",
"token": "meta meta meta meta meta meta.structure.dictionary.value string"
},
{
"foreground": "ff79c6",
"token": "meta meta meta meta meta.structure.dictionary.value string"
},
{
"foreground": "bd93f9",
"token": "meta meta meta meta.structure.dictionary.value string"
},
{
"foreground": "50fa7b",
"token": "meta meta meta.structure.dictionary.value string"
},
{
"foreground": "ffb86c",
"token": "meta meta.structure.dictionary.value string"
}
],
"colors": {
"editor.foreground": "#f8f8f2",
"editor.background": "#282a36",
"editor.selectionBackground": "#44475a",
"editor.lineHighlightBackground": "#44475a",
"editorCursor.foreground": "#f8f8f0",
"editorWhitespace.foreground": "#3B3A32",
"editorIndentGuide.activeBackground": "#9D550FB0",
"editor.selectionHighlightBorder": "#222218"
}
}
monaco.editor.defineTheme('custom-theme', data);
monaco.editor.setTheme('custom-theme');
};
// Check if Monaco exists
var codeEditorPoll = setInterval(function () {
var m = editor.call('editor:monaco');
if (m) {
loadTheme();
clearInterval(codeEditorPoll);
}
}, 500);
})();
- In the
loadThemefunction, you can use theme code from this repo: monaco-themes/themes at master · brijeshb42/monaco-themes · GitHub - Refresh the code editor tab
My favourite is Dracula 
