Since so many on this forum like to look at modern EFO's, I thought I'd post this color shift that I only noticed quite recently, even though I've had this plate block in my collection for years.
Notice the top 1/16" of each stamp (above the rifle) seems to have the yellow color incomplete. Strangely, the yellow color doesn't seem to penetrate into the bottom of each stamp. Although if you look closely you can see some slight color mis-registration on the banner that reads "United States Postage", too.

I know color shift errors were plentiful on the Giori Press issues of the 1960s and 1970s, but this one stood out enough that I thought I'd post it.