Ocarina of Time
The Guards seen in the throne room in Ocarina of Time wear royal purple breeches under their plate armor and graves. They also have more ornamental helmets with golden tips and purple spears. Several guards are depicted guarding the King of Hyrule in his throne room, which can be seen through the window in the Courtyard. If Link shoots a Deku Seed at the western window in the Courtyard, a Royal Guard will scold him. 
Several Guards with ornate shields protected Princess Zelda in Kingdom of Hyrule's last stand against the Twilight invasion. When the Shadow Beasts stormed the throne room, the Guards were violently slain.
Breath of the Wild
In Breath of the Wild, the Royal Guard wear an Armor Set known Royal Guard Set. They wear a blue and red Royal Guard Uniform with white gloves, a beret style Royal Guard Cap, and white Royal Guard Boots. In one of the Recovered Memories that Link regains, Royal Guards are shown standing around King Rhoam during his ceremony to entitle the Champion. During Recovered Memory #11 "Shelter from the Storm", while talking to Link as they wait for a storm to pass beneath a tree east of Scout's Hill near the Bridge of Hylia, Princess Zelda mentions Link has dedicated himself to the path of a knight of the Royal Guard like his father, before asking him what he would do if he realized one day that he realized he just wasn't meant to be a fighter but everyone said he had to be one due to being born into a family of the Royal Guard, would he have chosen a different path. According to Purah's Diary, Link was the youngest member to be appointed to Hyrule's Royal Guard which she refers to as the Imperial Guard of Hyrule Castle. 100 years after the Great Calamity, Link is the only known surviving member of the Royal Guard and after Dark Beast Ganon's defeat he returns to his role as Princess Zelda's personal knight and bodyguard. Unlike other members of the Royal Guard, due to his status as the hero chosen by the Master Sword and the Hylian Champion, Link wears the Champion's Tunic and Hylian Trousers instead of the Royal Guard Set. However one Royal Guard Set survived the Great Calamity, which Link can acquire during the DLC side quest "EX Royal Guard Rumors". During said quest, Link must read Super Rumor Mill EX: Volume 4 at the Riverside Stable. The author Traysi reveals that according to a former maid of Hyrule Compend Castle, the surviving Royal Guard Set can be found within Hyrule Castle and that she hopes one day that the kingdom is restored as she hopes that a Royal Guard in shining armor will come a sweep her off her feet.
Several Weapons and Armor of the Royal Guard are scattered around the ruined Hyrule Castle. The Royal Guard used Royal Guard's Swords, Royal Guard's Claymores, Royal Guard's Spears, Royal Guard's Shields, Royal Guard's Bows, Royal Guard Uniform, Royal Guard Cap, and Royal Guard Boots.
Concept artwork of Link wearing the Royal Guard Set from Breath of the Wild
- "The dignified uniform for Hyrule's Royal Guard. It's made of lightweight materials and is both stylish and practical. It's a rather rare find." — N/A (Breath of the Wild)
- "Hey you! Don't cause any trouble!" — Soldier (Ocarina of Time 3D)
- "Super Rumor Mill EX: Volume 4 [Read.] From the moment I wake to the moment I sleep, my mind is full of rumors. Even my dreams are gossipy! Traysi here! You fine folks keep up with dream rumors too, don't you? Well, this one's so good it might as well be a dream. Listen up, history buffs! This tidbit is about the brave soldiers who were tragically wiped out during the Great Calamity. The royal guards who protected the royal family! Amongst Hyrule's soldiers, only the best of the best had the honor of guarding the royal family. Apparently, the equipment they wore can still be found somewhere in Hyrule Castle. They say a former maid spoke of treasure near the Dining Hall, in the Guards' Chamber, and on the second floor. I do hope one day Hyrule Castle is restored to its former glory, complete with royal guards. Hmm... I wonder when a royal guard in shining armor will come sweep me off MY feet... Traysi's Recommendation: ★★★★★" — Super Rumor Mill V4 (Breath of the Wild)