what wbeaton said… however about color match, if the repaired joint is to be polished and left unfinished, the zinc filler will oxidize to a darker color than the AL, becoming readily apparent over time.
And a helpful thought about joint preparation and cleanliness…. when prepping and "Veeing" out a joint never use an abrasive in the last operation, always a clean file. Aluminum oxide contamination is your enemy!. Final clean up and to help scrub the zinc rod into the joint use a CLEAN stainless steel wire brush that has NEVER touched anything but clean aluminum. I keep a couple of the small stainless steel brushes neatly wrapped in aluminum foil just for this purpose.

Joe B