title: Unable to compile Magento 2 theme
body: <p>I am attempting to compile a Magento theme which uses Magento/blank as the parent, every I attempt this I am presented with the following error</p>
  
  <pre><code>[fsvuphkpwz]:public_html$ php bin/magento setup:static-content:deploy en_AU
  
  Deploy using quick strategy
  frontend/Magento/blank/en_AU            2163/2163           ============================ 100% %  1 sec               
  adminhtml/Magento/backend/en_AU         2104/2104           ============================ 100% %  1 sec               
  frontend/Magento/blank/en_AU            2163/2163           ============================ 100% %  1 sec               
  adminhtml/Magento/backend/en_AU         2104/2104           ============================ 100% %  1 sec               
  frontend/Magento/luma/en_AU             2179/2179           ============================ 100% %  1 sec               
  frontend/GladiatorFitness/Gladiator/en_AU 2069/2201           ==========================&gt;- 94% %   5 secs
  Compilation from source: /mnt/data/home/######/fsvuphkpwz/public_html/vendor/magento/theme-frontend-blank/web/css/styles-m.less
  error evaluating function `darken` The first argument to darken must be a color index: 2570 in _typography.less in _resets.less in _reset.less
  
  
    [Magento\Framework\Exception\FileSystemException]                                                                                                                                                        
    Cannot read contents from file "/mnt/data/home/#####/fsvuphkpwz/public_html/pub/static/frontend/GladiatorFitness/Gladiator/en_AU/css/styles-l.css" Warning!file_get_contents(/mnt/da  
    ta/home/#####/fsvuphkpwz/public_html/pub/static/frontend/GladiatorFitness/Gladiator/en_AU/css/styles-l.css): failed to open stream: No such file or directory   
  </code></pre>
  
  <p>All I have in _theme.less is as per below</p>
  
  <pre><code>//  Color nesting
  @page__background-color: "#fff";
  @sidebar__background-color: @color-gray40;
  @primary__color: @color-gray80;
  @border-color__base: @color-gray76;
  
  @link__color: @color-gray56;
  @link__hover__color: @color-gray60;
  
  //  Buttons
  @button__color: @color-gray20;
  @button__background: @color-gray80;
  @button__border: 1px solid @border-color__base;
  
  //  Primary button
  @button-primary__background: "#f15429";
  @button-primary__border: none;
  @button-primary__color: @color-white;
  @button-primary__hover__background: "#f15429";
  @button-primary__hover__border: none;
  @button-primary__hover__color: @color-white;
  
  //  Navigation
  @navigation-level0-item__color: @color-gray80;
  @submenu-item__color: @color-gray80;
  
  @navigation__background: @color-gray40;
  @navigation-desktop-level0-item__color: @color-gray80;
  @navigation-desktop-level0-item__hover__color: @color-gray34;
  @navigation-desktop-level0-item__active__color: @navigation-desktop-level0-item__color;
  
  //  Tabs
  @tab-control__background-color: @page__background-color;
  
  //  Forms
  @form-element-input__background: @color-gray89;
  @form-element-input-placeholder__color: @color-gray60;
  
  //  Header icons
  @header-icons-color: @color-gray89;
  @header-icons-color-hover: @color-gray60;
  </code></pre>