Asset Pipeline and Sprockets

Ok I would love to work out how to use the new Raisl 3.1 Asset
Pipeline with SCSS variables, mixins etc and being able to use the
asset_path tag.

What I have so far is this. Im my application.css.scss I have the

     *= require_self
     *= require layout
     *= require home

This works fine with using the asset_path helper and variable within
layout ie,

    // layout.css.scss.erb
    $main-color: #cccccc;

      background: url('<%=asset_path "small-avatar.gif"%>') no-repeat;
      color: $main-color;

But now in home lets say I want to use the variable from my layout.

    // home.css.scss.erb
      color: $main-color;

I get error.

    Sass:SyntaxError: Undefined variable. "$main-color"

I cant use the @import method as I will then not be able to use .erb
for the asset_path helper.

Has anyone managed to get both working together ??