Howdy
First of all, there is no official SAAMI approved +P pressure standard for 45 Colt ammunition. SAAMI does have guidelines for +P 38 Special ammo, but not for 45 Colt.
So any commercial 45 Colt ammunition that carries the '+P' label is going to be made to whatever pressure standard the manufacturer chooses. There is no guarantee it will be safe in all 45 Colt revolvers.
Now..............If you are talking about Buffalo Bore ammo, they go the extra mile. If you click on the 'more info' button on any of their 45 Colt loads, they will tell you what guns that particular box of ammunition can be safely fired from. They are very specific. Some of their heavy loads deliver more velocity while staying safely under the SAAMI Max pressure for 45 Colt of 14,000 psi. And they will tell you with other loads that they should only be fired in certain revolvers and not in others. The information is all there on their website.
Personally, and I know I will get guff for this, I would not fire any 45 Colt ammunition that is labeled +P in anything other than a large frame Blackhawk, 'old model' Vaquero, or one of the custom revolvers specifically designed for extra heavy loads. I most certainly would not fire it in a standard Colt or Italian replica that has similar dimensions to the Colt. Yes, others will say the modern guns are capable of more pressure than SAAMI Max pressure, but I won't do it in any of my 45 Colt revolvers that have the notoriously thin chamber walls of the SAA.