Verified it in the templates.less of isis and saw the results in template.css - after compiling

@hans2103 Can you try running the file /build/generatecss.php from your CLI?
That would generate the template.css file for the Isis template and it could be tested better.

error on compiling template.less by /build/generatecss.php

expected color value: failed at ../media/jui/less/accordion.less";
C:\xampp\htdocs\pbf\administrator\templates\isis\less/template.less on line 48
expected color value: failed at 16.5%
C:\xampp\htdocs\pbf\administrator\templates\isis\less/template-rtl.less on line 100

Compiled less in the isis templates.less - success after viewing source of template.css

1. try, more exactly now: before:
2. media.less attribute ".media .media" not existing in template.css of isis
3. compiling in the template and with help of generatecss.php did not change anything

after patch:

• compiling in the template worked
• adding a fake entry to template.css
• compiling with help of generatecss.php worked and fake entry was gone ;-)

  ---

  _{This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/6417.}

@Bakual
just run "php buil/generatecss.php" from CLI
the result is not what I expexted. See comparison below.
staging...hans2103:staging

I was expecting to see new css lines in template.css from isis template.
I notice an import of media.less in template.css

moment... I see what went wrong... typo main.less should be media.less. Oops

This PR can be closed since I've made a new Pull Request #6465 containing changed less and compiled .css files.
Thank you @Bakual for explaining me how to compile from CLI in your comment above. Didn't knew that was possible to do.
#6465