<%= form_for(@user) do |f| %>
  <% if @user.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@user.errors.count, "error") %> prohibited this user from being saved:</h2>

      <ul>
      <% @user.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %></br>
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :email %></br>
    <%= f.text_field :email %>
  </div>
  <div class="field">
    <%= f.label :time_zone %></br>
    <%= time_zone_select 'user', 'time_zone' %>
  </div>
  <div class="actions">
    <%= f.submit :class => "button" %>
  </div>
<% end %>

<%= form_for(@user) do |f| %>
  <% if @user.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@user.errors.count, "error") %> prohibited this user from being saved:</h2>

      <ul>
      <% @user.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %></br>
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :email %></br>
    <%= f.text_field :email %>
  </div>
  <div class="field">
    <%= f.label :time_zone %></br>
    <%= time_zone_select 'user', 'time_zone', nil, :include_blank => true %>
  </div>
  <div class="field">
    <%= f.label :color %></br>
    <%= f.text_field :color %>
  </div>
  <div class="actions">
    <%= f.submit :class => "button" %>
  </div>
<% end %>

Include blank in time_zone_select; add color form field
Include blank in time_zone_select; add color form field
