You have probably never ordered invitations before, right? Here are some tips.
1) Most invitations with light colored graphics and text/wording are actually invitations made with white card stock that have the background color printed on. Unless a special printing type is involved... like thermography or screen printing.
2) Square envelopes cost more to mail out than rectangular envelopes. This is a post office regulation. It's not a lot more, but, good to know.
3) Unless specified in the description, assume that graphics and text will not be printed with raised ink. For the most part, Save the Date Originals does not offer special thermography, screen, or foil printing.
4) Black or dark envelopes will be harder to write on- and so would response cards with a black or dark background! If you have an invitation with a dark background, have the designer come up with something that matches, but with a white background, for the response card.
5) You don't need to order as many invitations as you have guests. You can send one invitation per house hold, with each guest's name written on the envelope.
Almost every invitation set has something unique about it. Sometimes a customer will go with a folded rsvp card. Sometimes they will go with inner and outer envelopes. Sometimes a customer will pick an odd size for something unique. You have choices.