Since your Colt is a post-1972 gun, a limited amount of +P ammo will be OK.
With that in mind, the all time grand champ of .38 Special ammo is the +P 158 grain, lead, hollow-point ammo, variously known as the FBI, Chicago, St. Louis, New Orleans, LAPD, etc. load.
Also known to cops as the .38 caliber SPLAT. (For the sound it supposedly made hitting the bad guy).
A good second is the 125 grain jacketed, hollow-point.