I have a 55-year-old cut squared block stone house. The stone is in
need of tuck-pointing in some areas.

First off is it called tuck-pointing when it is not brick but stone?
The other thing is how do I go about to try to mix matching mortar? It
looks like a lot of aggregate (sand) was used in the motor.

Is there a good site about how to mix mortar to match old mixes? Or is
there a service where I can send a piece of the mortar and get a
formula for its mix. Because of its age am I actually seeing it aged
in color too and a pigment may be needed also? Is there mortar that is
only lime and no cement? Help!