Bright blue is a good spark, faint orange is probably the problem.
Voltage at coil while cranking is the critical measurement because the draw of the starter and any poor connections will show up then and perhaps only then. If the coil does not get enough voltage you don't get a good spark.
To check for spark and how good without cranking the engine remove distributor cap, turn engine so points are closed, open points manually several times while checking for spark from coil high tension wire/terminal to ground.
If this checks out good yet a weak spark while cranking you can look for poor connections or low battery.
If you have another good battery you can use it solely for providing 12V to the coil. Just another way to troubleshoot and track down ignition problems.
Grigg
