Rails: Filtering by adding/removing query string parameters

I have written the following code to create a UI that enables filters to be added and removed from the query string:

<% @colours.each do 开发者_Go百科|colour| %>
  <% if params[:colour].include?(colour) %>
    <% # Already being filtered. Show remove link. %>
    <% modified_params = params.dup %>
    <% modified_params[:colour].delete_if {|v| v == colour } %>
    <%= link_to "Remove #{colour}", modified_params %>
  <% else %>
    <% # Not being filtered. Show add link. %>
    <%= link_to "Add #{colour}", params.merge('colour[]' => colour) %>
  <% end %>
<% end %>

Clicking an 'Add' link adds the filter to the query string; clicking a 'Remove' link finds and removes the filter from the query string.

This works fine, but all looks rather messy to me. I am looking for suggestions to improve this code. Perhaps there is a better way to achieve this altogether, or maybe a gem that I have overlooked.

Any feedback much appreciated as I am relatively new to both Ruby and Rails.

Many thanks.

Update

Just to clarify, an example query string might be as follows:

?colour[]=Red&colour[]=Green&colour[]=Blue&size[]=Very+small&size[]=Small

Each filter link should continue to preserve other parameters that are present in the query string.

I would make a helper method, maybe "get_colour_link", and pass in your colours and params.