ASP.NET MVC Ajax form not routing values

This is a sister question from another question I posted (here). Many thanks to @nurdyguy and all of the people who helped me previously. However, I am having an issue where I am unable to pass a list of values to a destination controller that's in another View. My desired output is to send over the complete List object but right now I am getting a value count of zero (0) when it gets to the controller.

Here is my Model:

using System.Collections.Generic;

namespace Foo.Models
{
  public class FooViewModel
  {
    public List<Foo> FooCollection = new List<Foo>();
    /*Contains two properties
      string CarName {get; set;}
      string Color   {get; set;}
      List<Features> Features = new List<Features>();
    */
  }
}

My View

    @model Foo.Models.FooViewModel
    @{
var RedCars = Model.FooCollection.Where(c => c.Color == "Red").ToList();
    ... //{yellow, blue, green}
}
    <div id="FooCollection">
      <section class="no-padding-top no-padding-bottom">
        <div class="container-fluid">
          <div class="public-user-block block">
            <div class="row d-flex align-items-center">

              <!--Red Cars-->
                @using (Ajax.BeginForm("../Bar/Index/Red", null,
new AjaxOptions
{
HttpMethod = "post",
InsertionMode = InsertionMode.Replace,
UpdateTargetId = "CarsList"
}, new { id = "RedCarsForm" }))
  {
        <input type="hidden" name="Cars" value="@RedCars" />
          <div id="status-container" class="col-lg-3 d-flex align-items-center">
            <button type="submit">@RedAlerts.Count</button>
            <strong>Red Cars</strong>
          </div>

          }
          <!-- same structure for yellow, green, blue --!>
      </section>
    </div>

My Controller:

public ActionResult Index()
{

   foreach (var car in db.database.Db_GetCars())
   {
      model.FooCollection.Add(new Foo()
      {
         CarName = car.CarName,
         Color= car.Color
      });
    }
    return View(model);
}  
Destination Controller:

    namespace Foo.Controllers
    {
      public class BarController: Controller
      {
        BarViewModel model = new BarViewModel();

[HttpPost, Route("/Bar/Index/{color}")]
        public ActionResult Index(List<Foo> Cars)
        {
          //logic goes here

          return View(model);
        }
      }
    }

I spent some time digging around the best practices to route data but most places I've went have their forms set up like mine and it seems to work (for them). I even passed (as the second parameter) new { Cars = RedCars } but I still get zero (0). Is there something I am missing? Many thanks in advance!