From Zelda Wiki, the Zelda encyclopedia
The Hero's Trial's levels within the Silver, Gold and Hero's Doors are dark versions of the Sea of Trees, Talus Cave and Death Mountain, respectively. The third part of each stage ends with a shadow version of Vaati's Palace, resembling the Palace of Twilight.
To commemorate the series's 25th anniversary, a "25" design is worked into multiple areas of the levels. For example, one of the Talus Cave levels includes a set of panels viewable only be Green and a set of panels viewable only by Red, which together form the number "25".