THE BLACK HORSE - FAMINE (Revelation 6:5-6).
Famine is the second of God's sore judgments (Ezekiel 14:21). In Lamentations those who suffered famine were described as ‘their visage is darker than blackness, they are not known in the streets, their skin cleaves to their bones, it is withered, it is become like a stick' (Lamentations 4:8), and we are told ‘our skin is black like an oven because of the burning heat of famine' (Lamentations 5:10). We can compare with this Jeremiah 14:2 where the people sit in black on the ground because of the dire famine. So blackness is associated with famine.
The measurements of the wheat and barley also indicate famine, for men measure their food like this when hard times stare them in the face (Ezekiel 14:10; Ezekiel 14:16-17). In the time of the emperor Trajan a denarius would buy twenty times as much wheat as mentioned here, so that there is clearly a great shortage. But it is not quite starvation rations. So the black horse represents shortage and famine.
Yet the oil and wine is not to be hurt. Elsewhere we are told that the one who loves oil and wine will not be rich (Proverbs 21:17). This suggests that these items were seen more as luxury items. So it would seem that the idea is that the rich will not be inconvenienced. Only the poor will suffer. How true this has often been through history. But as Jesus stressed in the story of the rich man and Lazarus (Luke 16:19-31), the rich will one day be called to account. So the black horse represents the many shortages and famines that will bring such misery to mankind, starting from the first century onwards. These too God allows in His purposes.