I've just started out with the black arts too - with a second hand Remington .44 target. Take your time with load development - and don't be tempted by those who urge you to "stoke" up the load! So far my most consistent load is around 15gr by vol of Pyrodex P. With this load (using two hands) I can get 4/5 of 6 shots in the black at 25yds, with all on the target. I started at 25 Grs by vol and don't know where most of those shots went!

Sage advice above regarding time to take the shot. Once on target I start counting slowly in seconds, if I get to 5 the shot will be a waste due to wobbles so slowly down, take a few breaths and repeat. Eventually I get to pull the trigger.

A quick clean between reloads is also good advice - on my first few outings I suffered a few failure to fires because of not doing this (in ignorance!). Now each reload the nipples are poked through and the crud wiped off the cylinder and frame.

I'll be interested to hear how you progress with the Colt as that is likely to be my next purchase pistol wise. All the best.