Bro. Branham makes it clear from the quotes below that the mark of the beast is the lack of the Holy Ghost, THE SEAL OF GOD in a man's life,

I have not seen any reference to the mark of the beast being the color of the skin.

"Now, it's been said... And I hope that my colored friends that's in here will excuse this remark, because it's absolutely not right. The first time I ever met anyone in my life, after I'd been converted... I was--met Brother George DeArk and them down there. And I was walked, and the Lord led me to a little place. And they was discussing where the colored man came from. And they were trying to say that the colored man, that Cain married an animal like an ape, and through there come forth the colored race. Now, that's wrong. Absolutely, that's wrong. And don't never stand for that. 'Cause there was no colored or white, or any other different; it was just one race of people unto the flood. Then after the flood and the tower of Babel, when they begin to scatter out, that's when they taken their colors and so forth. They're all come from the same tree. That's exactly right. Adam and Eve was the father and mother, earthly, of every living creature of human beings that's ever been on the earth. That's right. Black, white, pale, brown, and yellow, whatever color you might be, that's absolutely the place that you live in, and the way that…" [Questions and Answers on Hebrews #3, Jeffersonville, Indiana, COD, 57-1006]

"Now, we find out that the first marking of a human being started in Genesis, Genesis 4:15. God marked Cain. That's where the first mark of the beast was ever put on, was put on Cain; he is the beginning of it. Now, you say, "Cain having the mark of the beast?" All right, let's notice.
Now, he said, "Thy seed shall bruise the serpent's head, and his head shall bruise thy heel." Watch the lineage of Cain. As Cain come down, become scientist, smart men, great men, on down like that. But the seed of Seth as it come down, become peasants, sheepherders, farmers. So you see, there is... Now, watch, the Bible said, "I'll put enmity (God did) between your seed and the serpent's seed." Now, so... Now, ministering brethren, just hold your peace just a minute. I--I know they always climb down my neck on this. But the Bible said that the serpent had a seed. That settles it. The serpent's seed, let it be any way you want to take it, we'll restrain from that; I got my idea too. But they--but le... Be whatever it will, the Bible said in Genesis 1, the--the first of Genesis, that the serpent had a seed. And now remember, the serpent was not a snake to begin with, a reptile. He was the next thing to a human being. Science has tried for thousands of years to find that missing link between man and beast. The closest they can come is to a chimpanzee. But they cannot get from the chimpanzee to the human being. Why? It was a serpent. Now, if you notice in Genesis 3:1, "The beast--the serpent was the most subtil of all the beast of the field." A beast, not a reptile. He was more like a man. He looked like a man. He was that missing link in between there, because that's the only way. The seed of a human will not coincide with the seed of a animal. But this fellow was the only one the devil could use because it was just between man and beast. And the genealogies... " [The Mark of The Beast, And The Seal Of God #1, Long Beach. CA, 61-0216].

"But if you hear the trumpet... See, hearing, faith cometh by what? Hearing. Now, not--not just listen with your ear, but if you hear that means you understand it, you accept it. "I hear you; I believe it." See? It's hearing. Stephen said, "You stiff-necked, uncircumcised in the heart and ears..." See, uncircumcised... They could hear it with the ears but uncircumcised, they couldn't believe it. See? Uncircumcised in the heart and ears, understand it. "Oh, it's all a mystery to me, like Cain. Take it or leave it. I joined church, that's as good as I can do." All right, Cain. You'll mark with the beast and go right on off in your denomination. But you can come to Christ and be sealed by the Holy Ghost. You can take your choice. You can take your choice. Now, watch. You hear the Gospel trump... What is the Gospel trumpet? The good news, the Holy Ghost is here. How do you know it is? Watch It work; see what It does. It's the good news. " [The Mark of The Beast, And The Seal Of God #1, Long Beach. CA, 61-0216].

"It shall be light in the evening time. That's right. While evening lights are shining, why don't you receive it? Why don't you come to it? Don't be sealed away. Don't set dead. Believe on the Lord Jesus Christ and be sealed into the Kingdom. What is the mark of the beast? To reject the Holy Ghost. See? The borderline... See? After he once come to the knowledge of the truth... "For it is impossible for those which were once enlightened..." See? Coming up to the knowledge of the truth, and seeing that they see the truth, and see the knowledge of it, and see it's here, see it working, see it's right, and have a knowledge of the truth and then turn away again, "There remaineth no more sacrifice for sin.” Just like Cain at the beginning, so will it be at the end. That's Hebrews the 10th chapter. And will be marked away from the Presence of God and be a Baptist, Presbyterian, or a Pentecostal, by denomination only, the rest of their days. They'll serve the denomination instead of serving Christ, serve their creed. Be a Catholic, be a Methodist, be a Protestant, or whatever you might be. But if you--not... If you're of Christ you're sealed with the Holy Ghost. If you're not, you'll be marked one of these days and just you'll cater to your organization; that's all you'll ever know and be condemned at the end." [The Mark of The Beast, And The Seal Of God #1, Long Beach. CA, 61-0216].

"And you go into a denomination, they say, "I know; we don't believe in This. Our bishops in our church teaches we are one of the oldest churches. We don't teach..." I don't care what they don't teach. If the Bible teaches it, the Holy Spirit in you, It'll feed on the Word. No matter how smart a man is and how he can try to explain it away, they can explain away. A infidel can take the Bible and explain God away from you. Therefore, no man has any right to preach the Gospel unless he's been like Moses, back yonder on that sacred sands where him and God alone stood, until a man's born again and stands there face to face with God, and knows. There's no infidel; there's no psychology; there's no explaining; there's no scholar in the world can take that away from you. You were there when it happened. Yes, sir. You know what taken place. Then you say, "I had that kind of experience, and I got a spirit on me." And if it denies the Word in any way, you got the wrong spirit. You say, "I--I can't go for this stuff like this, I know, but our church..." Oh, oh, there's a wrong spirit. There's your mark of identification. Cain, you're marked. Yes, sir. Eve just doubted one little Word, not all God said, just one little Word, and it caused every heartache and heartbreak, and death, and sin, and battles, and everything else, every grave, every ambulance ever screamed, every hospital was built for the sick. Her one little doubting one little Word of God caused all of this. And she was put out, when this never would've had to happen. How are you going to get in, doubting one Word of It? Say, "I know It says that, but It..." It means just that.." [Why I’m Against Organized Religion, Jeffersonville, Indiana, 62-1111E]