Black text on a green background
The expression "Some of my best friends are..." dates from around the 1940s and was often used to defend oneself from being seen as prejudice or to promote the type of associations that the wearer or user was involved in. In this case, "some of my best friends are (green)" could refer to the popular association with Kermit the Frog of The Muppets or someone concerned with environmental issues.
TVTropes. (n.d.). Some of my best friends are x. https://tvtropes.org/pmwiki/pmwiki.php/Main/SomeOfMyBestFriendsAreX