How to change a color on the Luma theme?

[TylerWolf]

Using this guide http://devdocs.magento.com/guides/v2.1/frontend-dev-guide/themes/theme-create.html I have created a child theme for Luma. 

I would like to change the color of the top bar. According to this https://magento.stackexchange.com/questions/102060/magento-2-page-header-background-color I should find it here app/design/frontend/Magento/luma/Magento_Theme/web/css/source/_module.less and move that file to my theme. I do not have that file at that location. Where can I locate it? And is that the proper way to make a theme change?

[KarlaSa]

You will find app/design/frontend/Magento/luma/Magento_Theme/web/css/source/_module.less file under

vendor/magento/theme-frontend-luma/Magento_Theme/web/css/source/_module.less 

[TylerWolf · Accepted solution]

The only thing in there for me is my child theme. Nothing else is in there.

Just want to add because I did a composer install the theme is in the vendor file. I have less files in the source files but modules is not there.

Edit: So I found it. For me it was under Magento_theme in the vendor file, not in the actual Luma theme. I do not understand why but this is where it is located.