I had a dream I was watching people go to hell ?

Simple, you see what's going on around you and what not to do. It's not your place to "save people" from damnation. 

Did it look white and grayish instead of the stereo typical red and black with fire?

I disagree with people saying it is your place to warn them. 

They should know already or come in contact with Christians in conversation.

The dream might mean you need to abandon the sources of entertainment and delights you have because they are dying out 

God does judge lol

Btw if you saw people go to Hell then you know the place exists without a shadow of doubt. Let not your heart be troubled.

I went to YouTube and I watched the videos from Mario Martinez, Mary Baxter and Bill Wiese. These people were in fact in hell for a short period of time for different reason, until the Lord brought them out and told them to warn the world.

The experiences and the observations of these three people are very similar, although they went to different parts of hell and saw some different things. 

Hell is shaped like a human being if you look at it from above and it keeps growing. It is located somewhere in the center of this earth. When people die they seem to fall through a black tunnel of sorts and as they descend they start hearing the screams of millions as flames become visible. There is no way out of there, and there are no second chances.

I could not sleep without the lights on after seeing their testimonies. You can see it on their faces, they still feel horror just talking about it.

Yes, I became a Christian and I read the Bible. I don't want to go there, and I wish with all of my heart that nobody goes there.

This topic is not funny. The horror and terror in that place cannot be fathomed.

If you have relatives, loved ones and friends that did not repent of their sins and receive Christ, they are on a train headed there. Your life on earth right now and right here is probably the only hope they have that someone will warn them.

Show them those videos, and lead them to repentance.

Tomorrow is not guaranteed for anyone.

Sorry to say, if you did nothing to save them. You will be judged for selfish act.