The 4 horsemen are 4 fallen angels, each given authority over 1/4 of the earth:
1. White / West - false Christianity. A distorted version of the gospel. Started by Byzantine Emperor Constantine the Great when he “converted”. Today Catholic and a lot of the Protestant Church too.
2. Red / East - Atila the Hun initially. Later the Turkish Ottoman Empire, and later the Soviet Union today Communism / Socialism.
3. Black / North - Rooted in Odoacer, the Northerner Goth who conquered Rome. Manifests in money loving Capitalism today.
3. Pale / Green / South - started with Mohamed ie Islam.
These 4 have been given power to take over the entire earth using 4 different methods. They started their work when their seals were opened. The 5th Seal is a long period (that’s why we are requested to be patient during this time) that we are currently in, whilst the 4 horsemen extend and consolidate their conquest of the earth.
Towards the end the White and Black merge ie already happening with Europe and America being Christian and money loving. Then the Red and Green merge, which will see the East and Islam falling under the same spiritual authority - yet to happen, I think. That’s the symbolism of the Sun (White) turning Black, and the Moon (Pale, Greenish) turning Red. There will be a corresponding literal sign in the sky, but the spiritual meaning is a consolidation of the 4 powers into two.
Compare to the camp of Israel in the Old Testament. Israel had to be protected North South East West, probably against attacks by the same 4 fallen angels.
Four refers to the scattering of Israel, towards the 4 “corners” of the Earth. The horsemen are to accomplish this; almost.