HTML to have cols
<col> # --> column for row headers
<% quantity.times do %>
<col> # --> column for data
<% end %>
CSS select even-odd columns
col:first-child {background: #FF0}
col:nth-child(2n+3) {background: #CCC}
CSS select even-odd rows
tr:nth-child(even) {background: #CCC}
tr:nth-child(odd) {background: #FFF}