Revelation 6 mentions the 1st horse white, 2nd red, 3rd black and 4th yellow.
That's also the description of the 4 races from the 4 corners of the earth.
The 2nd church of Revelation matches the 2nd horse color: Persecution/ red as blood.
The 4th horse which the horseman is Death matches the 4th church Thyatira because Christ says that he will kill with death:
23 And I will kill her children with death; and all the churches shall know that I am he which searcheth the reins and hearts: and I will give unto every one of you according to your works.
8 And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.