Ignition coil failing

Hi folks! Beautiful Fall day here in the Poconos! Simple question . . . what’s the standard test for a failing ignition coil? My old Accord ('89-5sp/460,000 miles/4 cyl with a carb). Symptoms . . . idiot light (battery) once in a while . . . new battery last May . . . flutter in idle and tachometer once in a while. I checked spark . . . at the plug it’s orange, not blue. Any quick checks? This IS the original coil, BTW. Rocketman