Web personalization edition and preview
Hello community!
We are working on creating a web personalization campaign.
We are using the templates that Marketo is offering us to do so. However I have a couple of doubts on the edition:

+ When I try to change the modal color, or the header color or the content background color, I get no result. Why is this so? If I would like to change for instance the grey background for a green one would I need to do it via HTML?
+ After making a few changes, I want to preview the result, I have downloaded the chrome extension but I get no result when clicking the "preview" button. Do I need to take more steps?
I have taken a look at this link in the documentation: Preview and Test a Web Campaign - Marketo Docs - Product Documentation
and I would like to understand how is the "Preview Web Campaign on Your Website" different than others. I need to insert this web campaign in an external website that is not created vía Marketo. Is this the option that I have to choose?
Thank you so much!