I think the first doublequote around "red" is terminating the string in the first part of your ? : expresion. If it were me, I'd verbose that out some:
<% if @tour_request.booked_datetime then %>
<span class="label">Confirmed For:</span>
<%= @tour_request.booked_datetime %>
<% else %>
<span class="label">Date and time requested:</span>
<%= @tour_request.daterequested %>
<% end %>
That way you're not so much mixing the markup & the ruby, which always winds up confusing me.
Also--having .booked_datetime and .booked_datetime_string methods seems odd--consider writing a format_date helper to use to make dates pretty if you need to get fancy.