app/views/devise/sessions/new.html.erb
<body style="background: #001f3f;">
<%= form_for(resource, as: resource_name, url: session_path(resource_name), :html => {:id => "msform"}) do |f| %>
<%= devise_error_messages! %>
<fieldset class="bigger-field">
<h3 class="fs-title">Login</h3>
<%= f.text_field :email, placeholder: 'Email' %>
<%= f.password_field :password, autocomplete: "off", placeholder: 'Password' %>
<% if devise_mapping.rememberable? -%>
<%= f.check_box :remember_me %>
<%= f.label :remember_me %>
<% end -%>
<div class="actions">
<%= f.submit "Log in", :class => 'action-button' %>
</div>
<%= render "devise/shared/links" %>
</fieldset>
<% end %>
</body>