The CS45 spring is painted green, like the one in the pic.
The CS9 recoil spring is painted dark red.
One of the previous S&W forum threads showing the recoil spring for the CS9.
Recoil Spring CS9
Out-of-stock at the moment, apparently, but here's another pic from Midway.
Smith & Wesson Recoil Spring S&W CS9C CS9S - MPN: 263210000
S&W mixes their recoil spring colors among both models and calibers. The color
may change with spec or vendor changes, too.
They also mix the colors of their magazine springs, and they may be different than the color used for the recoil springs, or they may not use any paint color. For example, the recoil spring for the 9mm 3913/908/6906 variants is painted green (but the mag springs are red) ... and the dual recoil springs for the .45 4513/457 are painted light blue (but the mag springs are unpainted).
In the case of the CS9, though, the last time I ordered spare recoil and mag springs from the factory, both of them were different shades of red. (The red mag springs are the same for the CS9, 3913/908 and 4040PD, BTW.)