Does all leaves on earth have individual facets/hues?

Leaves on a single tree are for the most part the same color (some may brown and die early; some that are new growth may be a lighter green or red, but they mature the same color).

Most trees.

Just like human beings, each leaf is unique. Each type of tree creates leaves with certain elements in common, like number of lobes, are they sharp or rounded, what color and size, etc. But beyond these basics, each leaf varies. Maybe because of the amount of light or water that leaf got.

@anartist- I agree with you on that each tree creates leaves with certain elements in common, but that in general each leaf is individual. I am not an artist but I have noticed the differences in the trees in our park and when I went fire fighting it gave me an awesome opportunityto view our forest up close.

Do all leaves on a single tree have the same color?...No
As you pointed out the environment is different for each leaf. Color in nature is wonderfully variable because of this.