It's kind of a generalized statement.
The "C" at the end of a smartphone model number designated CDMA which can be both Verizon or Sprint. When Straight Talk had few smartphones in their offerings, the "C" designation did mean Verizon as all their feature phones with the "C" designation did use Verizon. However, that is now a bit outdated as Straight Talk smartphones that have the "C" can now be either Verizon or Sprint.
The "G" designation which designates GSM, now can be either AT&T or T-Mobile. However, the vast majority of Straight Talk phones with the "G" designation use AT&T. Very few use T-Mobile out of the box. However, several of the newer GSM phones will use T-Mobile such as the Galaxy S4.
The red and blue maps are a bit outdated too. Generally, yes, the red map means Verizon but the blue maps could mean everything else, including Sprint, AT&T, or T-Mobile.
In the refurbished page for this phone, GulfGolfer52 (is this you?) has posted a nice list of what networks phones use:
answered 1 month, 1 week ago