What is this story I'm trying to remember, set in an alternate black and white dimension?

Question

I read this book, when I was young, about a kid getting trapped in an alternate universe. The alternate universe was a mirror image of the real world, but in black and white. The kid remained in colour, and I vaguely recall the colour being a crucial part to getting back home.

In the real world, there was some sort of catastrophe, where a group of children all went missing. It turns out they were trapped in the black and white dimension, but had been trapped for so long that they also lost colour.

I remember there was some sort of twist, but I can not remember what that twist was. I remember that one of the trapped kids managed to escape, but it was not who the main character suspected it to be; I do not think that was the 'big' twist, because I recall that in the last moments, the good ending went sour.

The book would have been around in the mid 90s, and it was in English. I am sure I borrowed it from a library, I'm Australia, should that mean anything. I was only a kid, when I read it, but I do not want to discount books you would not expect a kid to be reading; I was a bit more advanced than other kids of my age, in regards to reading and literature.

Answer 1

The querent has marked their story as a duplicate of Story about students stuck in a black and white universe, which would indicate that it is R.L. Stines's The Haunted School

On the night of the dance, Tommy and his friend Benjamin "Ben" Jackson need to fix a banner. While searching for needed materials, they find an elevator that goes sideways and transports them to a classroom in black and white world, a place where everything is in gray scale (black and white). Here they meet Seth Cortez and his friends, Eddie, Mona, Eloise, and Mary who became a few of the members of the Missing Class of 1947 who have not aged even after all that time. Seth tells them the story of how a photographer named Mr. Chameleon sent them to this colorless world in a "crack" with his camera, during the class photo. Everyone transported to this world gradually loses their colors.

...

Thalia explained to her friends how she opened her tube of lipstick one day and got excited after discovering that it still had color. She hadn't seen colors in so long, she tried to draw on the wall to make colorful pictures. But when her lipstick touched the wall, it made an exit into the real world. Thalia immediately went through it without thinking and the hole instantly closed, before she could go back for the others. She had tried to make another hole but the lipstick was only ordinary in the real world.