I was thinking the green (IF the gfx actually end up being green) could have at least two meanings- one being the obvious Eagles connotation, harboring the city's affinity for the team, the other being the positive connotation of the term "green" in modern parlance.
Also given the sheer size of the 3 in some of the new promos (even though I much prefer it's smaller usage in place of the "box" in the new logo), as has been said- it's definitely a testament to the "channel 3, channel 6, channel 10" mentality of the market. Aside from potential usage in the graphics and maybe on screens in the studio, I doubt the word "three" will be mentioned much, if at all, but for hardcore old-school Philadelphia viewers, just SEEING a three will perhaps help bridge that gap between the outgoing and the incoming.