Blue essentially follows decoration of room in gold (6)
I believe the answer is:
ormolu
'room in gold' is the definition.
'ormolu' can be an answer for 'gold' (I have seen 'Mosaic gold ' mean 'ormolu' so perhaps 'gold' could also mean 'ormolu'). I am not sure about the 'room in' bit.
'blue essentially follows decoration of' is the wordplay.
'essentially' means to look at the middle letters.
'follows' is a charade indicator (letters next to each other).
'decoration' becomes 'orm' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'of' becomes 'o''.
The middle of 'blue' is 'lu'.
'orm'+'o'='ormo'
'lu' after 'ormo' is 'ORMOLU'.
Can you help me to learn more?
(Other definitions for ormolu that I've seen before include "Gold-coloured alloy in furniture decoration" , "Gold-like decoration" , "Mosaic gold" , "Decorative gilt alloy" , "Gold-coloured alloy used in ornamentation" .)