grammaticality - Plural or singular when comparing two different objects?

Should I use plural or singular when comparing two different objects? For example, I want to tell a friend that I have two clothes that are of different styles but have the same color.

"The colors of shirt-A and shirt-B are blue."

or should I say,

"The color of shirt-A and shirt-B is blue."

or maybe even the following?

"The colors of both shirt-A and shirt-B are blue." vs "The color of both shirt-A and shirt-B is blue."