I assume you mean the background of the main workspace where flows are created?
To do that you should:
- create a file called
style.css (or whatever you want it to be called).
- in that file, add the custom CSS to modify the workspace colour - replace
red with whatever colour you want.
red is probably a bad choice...
- edit your settings file, find the
editorTheme section that should already be there and add a
page section under it:
Make sure you change the
/absolute/path/to/custom/css/file to be the absolute path to the file you created just now with the custom style in.
- restart Node-RED.
There are other options to customising individual instances without changing the colour. For example, you could change the title in the header with:
title: "Node-RED On Machine A"