An intriguing question: Is it possible to differentiate between the three nephews, Huey, Dewey, and Louie, by their individual behaviour and specific actions? Carl Barks furnished some of the Beagle Boys - who are another group of seemingly identical brothers - with special characteristics and preferences (see more HERE), so maybe he did the same with the nephews!? The sub-pages take a look at this question and maybe a conclusion can be reached...

Important notes:
In the sub-pages the brothers each have received their own page, in which all of their clearly identifiable acts have been registered. This includes all of Barks' stories and each occurrence has a brief description attached. It is important to notice that only iron-clad occurrences - in which you can connect a name with an appearance - are included which means that the nephews have to be clearly addressed in the panels. No deductions that may from time to time occur in the stories are admitted such as in U$27 The Money Champ where they name each other by pointing; it is impossible to judge who is who in the panel.
A seemingly secure way of determining who is who might be to judge by the nephews' cap colours, but this is not the case! Remember that Barks drew all his stories in black and white. Different artists at the publisher's office would then add colours as they saw fit. You can see Disney's official version of which nephew carry which colour cap HERE (bottom section).
The sub-pages are listed in a rather tight presentation. Thus it is necessary to know the stories by their original, American issue codes (see more HERE) as no additional, explanatory titles or comments are given. The stories are presented alphabetically after issue code, and the number following the codes (i.e. after the hyphen) reveal the page in the story from where the individual comments are taken. If you are in doubt as to which story a certain comment derives from, you can go HERE and brush up on your Barks knowledge.