In the many Tom and Jerry cartoons that have aired on Boomerang as well as syndication years ago, I have noticed that Tom's color has changed. In the early cartoons, he was grey, later cartoons he was bluish-grey and in the 60s and 70s cartoons he was blue. Anyone notice the color change?

Yup, thats cause the paint was simplyfed to make the cartoons cheaper

In the 1940s and '50s, Tom's fur was bluish-grey; in the 1960s and '70s, his fur was completely grey.