Cold-Blooded is rather versatile, as any weapon or play style can benefit from not being tracked. However, it reaches its full potential when used with a stealthy and mobile weapon, such as the Carbon Roller or Octobrush as it can enhance the sneakiness of a weapon, facilitating ambushes. A loud or otherwise conspicuous weapon may give itself away to surrounding enemies, no tracking needed.
In version 4.3.0, Cold-Blooded was retired, and its effects got combined with Bomb Defense Up to make a new ability: Bomb Defense Up DX. The default ability of all gear with Cold-Blooded (except the Gray FA-11 Bomber, Pearlescent Crown and Fringed Loafers) was changed to Main Power Up, while existing gear with the Cold-Blooded ability was overwritten with Bomb Defense Up DX.
▲ Preexisting mains changed to Bomb Defense Up DX.
— Items originally with Cold-Blooded as a main can be repurchased with Main Power Up (aside from gear unobtainable from SplatNet 2, which have Bomb Defense Up DX).
▲ Preexisting subs, ability chunks, and drink tickets changed to Bomb Defense Up DX.
Trivia
In Splatoon 2, Cold-Blooded was the only ability that was favored by two brands.