Often, when Det. Jane Rizzoli pulls her pistol, there is an audible sound of the hammer being cocked. However, her sidearm is a Glock 19, which does not have an external hammer; the only way to cock the internal hammer (called a "striker") is to move the entire slide rearward.
Massachusetts does not paint curbs red to indicate "no parking." This is done in the relatively snow-free Southwest, as in Calif. The opening shot of the "Boston" P.D. has its curb painted red.
Throughout the seasons with Casey, he is a Lieutenant Colonel (grade O5) in the Army. When he decides to marry the military instead of Jane, it is because he is "in line to become a General". As an O5, he would need time as a Colonel (O6) before being considered for Brigadier General (O7) but, as an O5, everyone would already know if his career track might go that far - for example, he would've attended or have orders to attend Command & General Staff College or the Army War College.
Forensics usually wear full protective gear to avoid cross-contamination and potential hazards, as anything else is not only highly unsanitary, but also an OSHA violation. However, whenever Maura is visiting a crime scene, she is always wearing casual clothing and only a pair of forensic gloves.