Hi there,
To change the colors after importing the demo content you will need to go to X > Launch > Options.
There you will find set of options to change the colors of different sections of the website. For example, the Layout and Design section is for changing the background.
You have options for buttons and Typography and so on.
Another step is to go to X > Launch > Templates > Colors, to change the main coloring schema of the theme from there.
And the last step will be to go to the pages one by one and check the individual elements and change their colors if there are still cases you see not matching with your desired one.
Thank you.