Change back color of every row of a table in ruby on rails

I want to change the backcolor of every rows of a table but I am not quite sure what is the best way to do it. Personally, I want to change on backcolor with ruby codes,but i dont know how :(

here is my code:

<% @word.each do |w| %>
                <% i=0 %>
                <% i=i+1 %>
                <% if i % 2==0 %>
 ........

Thank you for your helps

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Use cycle it's exactly what you need.