I thought I should give this a better explanation and why this translation is slightly wrong.
First of all this sentence and Alexis' reply is a reference to this dress:
People have had troubles discerning the colours of this dress, some calling it blue and black, others calling it golden and white. This depends on your screen settings and the lighting in your room.
First of all, "gylden" is a slightly dated version of the word "gyllen", stemming from "gull" (gold). An archaic spelling of "gull" was "guld", which explains the "d" in "gylden", while "guld" is not found in any modern literature. "Gyllen" reflects the modern spelling "gull" better.
Secondly, "gyllen" is the wrong translation in this case. From the english sentence "Golden and white", golden can be translate to both "gyllen" (an adverb) and "gull(gul)" (an adjective) [literary: golden yellow]. It is clear that "golden" in the english sentence represents the adjective describing the colour of the dress, so It should translate to "Gullgul og hvit" or "Gull og hvit". (Or "Gull(gul) and kvit" if you want to use an alternative spelling of "hvit".)
On a sidenote "gyllen" can also mean "shiny" and "gilded".