For any special event, the envelope that your invitations or save-the-dates are mailed in is the first indication your friends and family will see of your event. From traditional white to colored envelopes and colored ink — there are a plethora of options to work with. What's also important to keep in mind is the technical aspect of the envelope as well, since it is a working item that must also work within the confines of the United States Postal Service's requirements. After all, you do want to have each and every envelope arrive safely to their destinations.
Take into consideration some of these tips when choosing colored inks and/or colored envelopes. If you are not located in the U.S., make sure to check with your local post office on your country's postal requirements.
1) Make sure that there is enough contrast between the ink of the addresses and the envelope color.
2) Our trusty USPS would much prefers that black ink is used, however they do allow for some flexibility in using these inks colors: Brown, Gold, Crimson, Blue, Grey and Purple.
3) If your envelopes are dark in color, consider a white or light-colored calligraphy.
4) Remember that hand-canceling is an option if your envelope contains invitations with delicate details. It's important to check with your local post office if they are willing to do this for your invitations.
The following are samples of colored envelopes and inks that works with the USPS' addressing requirements.