Ok, in cambridge dictionary
of: preposition (MADE OF): made or consisting of; having:
dresses of lace and silk
plates of gold and silver
a land of ice and snow
a woman of great charm
a subject of very little interest
in /ɪn/ ●●● S1 W1 preposition
18: used to say what colour something is or what it is made of
Do you have the same pattern in blue?
a sculpture in white marble
SO, based on the dictionaries, we can say "a plate of gold" & "a plate in gold". "I ordered a dress in cotton" & "I ordered a dress of cotton"
What are the differences between "a plate of gold" & "a plate in gold"?