undistinguishable

The two colors were so undistinguishable that I couldn't tell which was which.

这两种颜色太难以区分，我分不清哪个是哪个。

After years of copying, the original painting and the fake became undistinguishable.

经过多年的仿制，原作和赝品变得无法分辨。

The view was so dark that the path was undistinguishable from the forest floor.

天太黑，小路与森林地面难以分辨。