Thanks for the theme name…I just moved this topic to the Luminescence forum.
Now I can help you out with your question about the font/text….
First important item to note is that any modifications that you need to do outside of the theme option settings should be done with a CSS Editor plugin if only css is being modified, or if you are changing other code, then using the child theme method is best. This allowed theme updates without losing any changes you do because these changes would be done from the child theme which inherits the parent theme. There’s a tutorial about this.
For font size, the base font size for this theme is 16px, and font sizes for other parts of the page is relative to this size. So if you change the body size, this will affect all other text in your site and pages. If you need to target a specific part of a page, then you will need to find the id or class of that container and create a custom font size for that container.
The other option is to use a Font plugin which lets you modify the font family, style, size, etc.
But for changing colours, the theme option settings in the theme should handle most if not all of that for you: Appearance >> Customize >>