Magento2 – Setting Main/Primary Color Value in Luma Theme

As you already figured out how to use the variables, I'll briefly explain the 2 ways recommended by Magento to override or extend the styles from a parent theme:

1. Simple way

• Extend:

  In your theme directory, create a web/css/source sub-directory. (You've already done this part)

  Create a _extend.less file there. According to the documentation: "Extending a theme using _extend.less is the simplest option when you are happy with everything the parent theme has, but want to add more styles."

• Override:

  Instead of creating the _extend.less file, you create a _theme.less file.

  In this case you need to copy all variables you need from the parent _theme.less, including those which will not be changed. Then make your changes.

  Drawback: "You need to monitor and manually update your files whenever the parent’s _theme.less is updated."

2. Structured way

• Extend

  This method lets you organize your code in a better way. Your changes will be structured. Instead of using a single _extend.less file to include all your changes, you create a extend file for each component from the Magento UI library you want to change.

  Say you want to extend styles from button and navigation components. In your theme directory create 2 files:

  _buttons_extend.less and _navigation_extend.less, then add your changes for each component in the corresponding file.

  Then you create the _extend.less file adding this code:

  • @import '_buttons_extend.less';

  • @import '_navigation_extend.less';

• Override:

  In your theme, create a copy of the file corresponding to the UI component you want to change _buttons.less, _navigation.less etc This file will override the _buttons.less of the parent theme.

It is important to notice the difference between override and extend.

You can read more at: http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/css-guide/css_quick_guide_approach.html

The files that make up the theme are located in vender/magento/theme-frontend-luma.

For customization, you don't have to copy over any file other then the ones you want to change. By creating a child theme with Luma as the parent, you will already have all those file using Magento's inheritance system.

Just note that as you do overrides, you have to follow Magento's naming convention, not the actual file paths. When you look at the Luma theme, you will see how they are doing this, just follow the same naming convention in your theme.

So say you want to customize the catalog xml layout file. The file lives in the Luma theme here:

vendor/magento/theme-frontend-luma/Magento_Catalog/layout/catalog_product_view.xml

For you, that same file will live in:

app/design/frontend/{{vendor_namespace}}/{{theme}}/Magento_Catalog/layout/catalog_product_view.xml