Change universal font for text in BigCommerce site

The default text on regular pages (such as the home page), text on category pages, and product pages is a light gray color and the purpose of this project is to change this universal sort of font setting to a darker shade of gray: 25% darker gray than the current light gray color (25% more dark, as in, 1/3 between current light gray color, and black). See as examples: Text on the home page [login to view URL], click on the "About Data Alliance" The text on product pages: [login to view URL] So, you will change the font color as described above, for all product pages, the home page, and text that I add for product category pages.