Each colour corresponds to an aspect of Tamazgha, the territory inhabited by Berbers in North Africa:

blue represents the Mediterranean Sea and the Atlantic Ocean;
green represents nature and the green mountains;
yellow represents the sands of the Sahara Desert.

The yaz (ⵣ) symbolizes the "free man", which is the meaning of the Berber word amazigh,
the Berbers' own name for themselves (endonym). It is in red, the colour of life,
and also the colour of resistance.

The Berber flag thus symbolizes the entire Amazigh people, living in harmony with their land, Tamazgha
(Source: Wikipedia - https://en.wikipedia.org/wiki/Berber_flag