After you leave the Fishing Pond with the stolen rod, run to the nearest body of water and enter it then exit it, then press Start twice. After that, press Start once more and go to the subscreen with the C button items, and assign the pocket cucco (which you get from the slim pretty looking red haired lady next the the chicken coop in Kakariko Village) to C-Right, and your bottled fish to either C-Left or C-Down, then unpause. After that you must release the fish from your bottle, then catch it again in the same bottle, then backflip by pressing Z then pulling backwards on the Analog Stick and pressing A. While Link is in mid-jump, press the C button that the bottled fish is assigned to and then immediately press the B button, which will show a Deku Stick. If you did it right, the B button will now show an empty bottle. Catch the fish in the bottle that's on the B button. You should now have the Secret Colored Gauntlets. After that, simply press start once more, go to the equipment subscreen, and re-equip the Master Sword
The colour of the Secret Colored Gauntlets is determined by the following:
Nothing = Black Gauntlets
Goron Bracelet = Green/Kokiri Gauntlets
Silver Gauntlets = Blue/Zora Gauntlets
Golden Gauntlets = Bronze Gauntlets
*All the Secret Colored Gauntlets have the same strength as the Golden Gauntlets, and getting the Silver Gauntlets or the Golden Gauntlets (you'll likely already have the "Goron's Bracelet") will override whichever Secret Colored Gauntlets you currently possess, so make the most of the Secret Colored Gauntlets and get the Double Defensive power-up from the Great Fairy of Courage that reduces enemy or environmental damage by half well earlier than is normally possible. You could have them (and Biggoron's Sword) before you have even entered the twattin' Forest Temple! Key-Uh-Uh-Uh-Uh-Uhhh
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If these wings could fly, we’d remember tonight, for the rest of our lives