What does the color gold symbolize in Macbeth? How is it significant?

Different colors symbolize different things in Macbeth. For example, the color red represents blood of the murdered characters and guilt which arises from the committed murders.

As far as the color of gold is concerned, it represents praise, power, preciousness and royalty. I will list three quotes from Macbeth where we can observe the usage of the adjective "golden."

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  I have bought
  Golden opinions from all sorts of people,
  Which would be worn now in their newest gloss,
  Not cast aside so soon.
  

  
  

Here, Macbeth talks about the praise and admiration he has received from all the important and powerful people, including the king himself, who promoted Macbeth to become thane of Cawdor.

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  That I may pour my spirits in thine ear;
  And chastise with the valour of my tongue
  All that impedes thee from the golden round,
  Which fate and metaphysical aid doth seem
  To have thee crown'd withal.
  

  
  

Here, Lady Macbeth talks about the primary goal for Macbeth -- that he must seize the "golden round." The word "round" means "crown," so the color of gold represents royalty and supremacy.

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  Here lay Duncan,
  His silver skin laced with his golden blood...

  
  

Here, Macbeth describes Duncan's blood as "golden," which means that Duncan's blood is royal, therefore, it is extremely precious because he is the king of Scotland.