Less variables are not replaced when compiling and error occurs

I am using less for the first time and I am having some problems. It's a MVC project and I'm using dotless and System.Web.Optimization.Less .

I have registered a bundle to include all my files less and return a single minimized file to the browser.

         bundles.Add(new StyleBundle("~/Content/Less").Include(
                 "~/Styles/Layout/Colores.less", 
                 "~/Styles/Layout/Global.less"));

As you can see, I am including a color file that contains the variables that define them, so that they can be used later in the rest of the project's less files. I also include a file to define the global style of the application that uses these variables ..

But when I go with the browser to the page, the less generated file contains the following error:

    /* Minification failed. Returning unminified contents.
      (54,12): run-time error CSS1036: Expected expression, found '@colorBlanco'
      (83,15): run-time error CSS1035: Expected colon, found ';'
    */

My Color.less file has the following content:

    @colorGris:         #808080;
    @colorBlanco:       #FFFFFF;


    /*Bordes*/
    @colorBordeInput:       #b1b1b1;
    @colorBordeContainer:   #E9EAEC;


    /*Sombras*/
    @colorSombraInput:      #a5a5a5;
    @colorSombraFocusInput: #81005D;



    /*******************
      ****  Layout ****
     *******************/
        /* userDataLine */
        @colorNombreUsuario: #700056;

What is the problem? If I see the file global.css file that is automatically generated in Visual Studio if I see that the variable has been changed by its corresponding value, for example:

#whereIAm #titleAndPath span {
  color: #ffffff;
}

Thank you!