I’m wondering if I can write my own small script (JS, JQuery), for example, to change the background color and embed (connect) to another site.
For example, there is a site http://example.com/
background color is red, can I somehow connect the script to change the color to green, let's say. How to start searching in this direction?
script
tag there, then you can make the changes you need. - Dmitriy Simushev