Double Color Cancel, How It Works?

As seen in the picture the 7 is in red, while the rest is black.
Found it strange enough to post it, since I do not see the point for the usage of the red color.
Also, there is no year on the cancel is that common practice?

It could either be deliberate to create some added interest in a philatelic item, or it could simply be picking up another color ink when re-inking the pad.

What an interesting and unique item! I have never seen one like it.

There is a year on the cancel, it is just so faded as to be almost invisible, and it looks to me like it was also red. They were probably using a nearly dry ink pad to ink their stamp.

Fairfax, VA post office. I'll be driving by there on the way home from work. LOL.

Edit: Rated 1.5 stars out of 5 for poor customer service on Google Reviews.

This appears to be what is called a "Pre-Inked Stamp" as described on the rubberstamps.com site as "Pre-Inked stamps, as implied, come pre-inked. There are several ways they are made, but what it boils down to is this: The stamps themselves hold the ink in the rubber. The ink travels through the pores in the stamp and when you press down on the stamp the ink is transfered to the paper. If you do a lot of stamping all at once, you may not want to use a pre-inked stamp. The ink takes a while to travel through the pores of the rubber."

To make the cancel above, the PO clerk used a "7" from a set of red-inked slugs in their black-inked handstamp. This is not a matter of using any ink pad at all. These bi-colored cancels are fairly common.

Thanks for the info John, that was very interesting.

John - I considered the pre-inked stamp also, I use one at work (has a red box and check mark on left, blue 'completed' on right). But the PO would need one which had changeable numbers and I could not see how they could change the date every day on a pre-inked stamp.