So how do clones tell each other apart?

I can kind of see it when they are wearing armor, if there was some sort of computer chip in the armor that others can read with their helmets, but other than that, how do they do it?

 

Very carefully.

 

The same way the parents of twins do? Helped by differing armor, tags and facial hair, I imagine.

There seems to be plenty of small genetic differences already, so tiny physical differences aren't out of the question either.

 

For a more serious answer, it's explained in several EU works that clones, while they look alike, tend to have very different personalities. (Also, Jedi can sense very clear and distinct differences between clones in their Force auras.) When they're in the trenches together, they get to know each other very deeply very fast, and these different personalities and character straits really stand out to other clones. Also, raised in an environment like Kamino, they learn very early on how to notice minute differences like facial expressions, body language, gait, etc.

 

Identical twins, triplets, etc. are (naturally occurring) clones and their families and friends manage to tell them apart.

 

Heightened sense of smell?

"Smell that brothers? Smells like Commander Rex is on his way!"

 

The point about twins is certainly true, though it may get a bit tricky once the number increases drastically. It's one thing to tell apart two or three identical looking persons, but once you reach tens or hundreds of people, you will get confused very fast.

 

Presumably, the HUD display in their helmets identified ID numbers.

 

I have my doubts that a single clone would be in contact with a significant number of clones in his lifetime. A clone trooper could easily be able to tell his squadmates apart, and his superiors, and they'd learn to identify their new squadmates when they rotate.

Those scenes with hundreds or thousands of soldiers on the battlefield, like Geonosis or Christophsis, I doubt each clone knows every other clone.

 

They mentioned in one of the issues of Dark Horizons - Loathing that they all have a heightened sense of smell. I believe that the example used in text was something that one of the clones smelled more like creamed corn, while the other was boiled corn.

 

So I was right!