XD : How to Import Assets (Colors & Character Styles) from one XD file to another

Is there a way to easily import Assets, specifically Colors and Character Styles from one XD file to another? I'm making mockups for 2 different websites that will use the same color and character style assets, and it would save me a lot of work if I don't have to remake these for each site and each new mockup I make for those sites in the future.

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