I know color misregistrations were common in these stamps from the 1970's, but this pair, in particular, shows quite a significant color shift visible from the words "US" to the yellow in the sun, to several of the components of the Skylab ship itself:
Yeah, the Giori Press issues were notorious for lax registration. The Skylab and Pioneer stamps were especially bad. It actually takes a few minutes of looking around before you can find a copy that is "properly" registered. I remember using up globs and globs of those 2 stamps, searching for a well-registered stamp to put in my collection.