[turnipla]

That’s called CSS. Use a user style, not javascript. The query is not applicable since its not offered by HN themselves.

[stragies]

You are misunderstanding what grease-monkey can do, and what I'm proposing.

e.g. try loading news.ycombinator.com?myColorVar=44ff55 , it will load normally, as usual. Of course, this variable means nothing to the HN backend, but this is where e.g. Grease-monkey comes in: It injects a bit of javascript of your choosing into the page context for the news.ycombinator.com/* pages. This scriplet can easily change the color of the header-bar, and add the colorVariable to all (non-external) links.

Of course, you can add a line like the following to your local userContent.css:

@-moz-document domain(news.ycombinator.com) { #hnmain>tbody>tr:first-of-type>td { background-color: lime !important; }

, but this has the disadvantage of requiring a Firefox restart for each change, whereas my method requires only twiddling the value in the URL, and it's valid for all future requests, until you change it again.

I hope, the above makes it clearer, what I meant the post above

[stragies]

The following code snippet in a grease-monkey-script with

// @include https://news.ycombinator.com/*

in the header will color the top-bar on HN pages with the color given in the URL such like https://news.ycombinator.com#MYC=lime or https://news.ycombinator.com#MYC=#ce1c01 .

(function() { if (color=document.location.href.match(/#MYC=(.)/)[1]) { document.querySelector("#hnmain>tbody>tr:first-of-type>td").setAttribute("bgcolor",color); document.querySelectorAll('a[href^="https://news.ycomb"],a:not([href="/"])') .forEach(e => {e.href+="#MYC="+color}); } })();

This script colors the top bar, and adds the custom colour to all HN-internal links, so until you manually change the URL, further navigation in that tab within news.ycombinator.com will retain your chosen top-bar colour.

(I hope the code comes out formatted in a legible way)

[turnipla]

You’re missing the point of the query. What’s the point of using the query at all?

OP suggested it as a way for users to customize their HN color; Then you suggested to take this query and make an extension out of it.

If you want to customize your HN color, use CSS, not this roundabout way through a query parameter.

The query never makes sense anyway. If HN were to allow customization they’d allow it in the options, not as a random query that you have to set manually.