A flag works something like a country's identity card. It says who the people are and where they came from, and during a revolution it does more than that: it becomes the thing you rally behind and the thing you can be arrested for carrying. Algeria and Angola both came out of long independence wars, and both encoded that experience directly into their flags, but they chose to say very different things with the space available.
Algeria
The Algerian flag came out of the struggle against French colonial rule. Green stands for Islam, the dominant religion. White signifies purity. The star and crescent represent the unity of the nation under Islam.
During the Algerian War of Independence the flag was not only a symbol of the future state. Carrying it was itself an act of resistance.
The Flag of Algeria
View Flag →Angola
Angola's fight for liberation from Portuguese rule was long and costly, and the flag reflects it plainly. Red and black stand for the blood shed for independence and for the soil of Africa. The machete and gear represent agricultural workers and industry, the two groups the new state expected to build its future on.
The design also had a job to do at home. Angola contains many ethnic groups, and the flag was meant to give all of them a single thing to stand under.
The Flag of Angola
View Flag →Two different arguments
Put the two side by side and the difference is in what each chose to emphasize. Algeria's flag uses color to make a claim about faith and purity, tying national identity to religion. Angola's puts tools on the flag and makes a claim about labor and economic future.
Both are flags of anti-colonial struggle, and both were designed by people who knew what they were fighting against. What separates them is what they thought would hold the country together afterward.