#1. Determine your Blog Page layout
Edit BLog Page > Edit Section

At Layout, your Blog page layout will be shown
In my example, the Blog page layout is Single Column

#2. Click on the Site Styles icon in the top right of the Header

#3. Choose FONTS

#4. Next, choose Assign Styles

#5. Scroll down to Blog: Single Column – Excerpt, and click on this option

#6. Edit Size and Style to change your Blog Excerpt font
