syfycity:

Can anyone identify Picard’s uniform in this scene? I’ve never seen it before.

http://syfycity.tumblr.com

It’s just a more casual undershirt. It’s usually seen when Picard is off duty. Their uniforms look heavy enough already so it’s hard to image there being anything underneath besides underwear. The gray undershirt first appears in Season 5, Episode 2, Darmok; where Picard is stranded on the planet with Dathon. In that episode he pulls open the red jacket where we see the gray undershirt for the first time. But I think it’s strictly a variant of Picard’s uniform only. There’s a few episodes late in the series where he can be seen walking around with the red jacket open, gray underneath.

Source: I’m a nerd and obsessed with TNG.