▲第二句是对的。即：

Are Africans a coloured people? 非洲人是有色人种吗？

这里的 people 虽然翻译成“人种”，其实还是指“人”，所以它的用法与表示“人”的people用法相同（永远表示“复数”意义）。如：

Africans and Indians are coloured people. 非洲人和印第安人是有色人种。

Black communities spoke up to defend the rights of all people of color. 黑人社团为捍卫所有有色人种的权利大声疾呼。

Coloured people were not allowed to use the same facilities as whites. 以前不允许有色人种与白人使用同一设施。

▲注：people 表示“人”时，是可数名词，根据需要可以连用不定冠词或用复数。如：

The French are known as a food-loving people. 众所周知，法国人是热爱美食的民族。

He described them as a virtuous and hard-working people. 他将他们描述成一个品德高尚、勤劳善良的民族。

Our Parliament has been a beacon of hope to the peoples of Europe. 我们的国会一直是欧洲各族人民的希望之灯。

Customs similar to this one are found among many peoples of the world. 在世界上许多民族中都有类似这样的风俗。