I might be stretching things here, but you can get to something close to subjective reality in scifi by imagining that, in the future, most everyone retreats into their own cyberspace worlds. In each perceived cyberspace world, the reality of that world might be different, and if you wanted to look at things a different way, you could.

Trees in a character's world would really only be cybertrees, but to people growing up in cyberspace, it might mean as much to them as real trees do to us. Neighbors in a cyberworld might have their viewpoints customized differently; to this person, trees are green, but for that person, trees are red. This allows for full subjectivity on every aspect that keeps the relationships between objects consistent.

If you wish to change your subjective viewpoint on issues that change relations between objects, you can always do the equivalent of moving to a new server, where trees float instead of remaining rooted to the ground. This means that you can have full and complete subjectivity of reality -- at least, the reality of each person's cyberspace world they inhabit.

Anyway, maybe this is not what you are looking for, since it keeps objective reality intact, and only introduces subjectivity to cyberspace. But I thought it might be useful anyway, since you mentioned in the original post that you asked the question for a novel you are writing.