You're referring to the aircraft's livery, yes, it is. The plane itself is the exact model(among others) operated by Southwest Airlines.
The 737-300 is no longer in production, and has been replaced with the 737-700 model. Southwest has a large number of the -700 in it's fleet currently.
The 737-800 is the replacement for the 737-400 model; the latter is also no longer in production.