Color Scheme change

Hi,
I am just looking to change the Text color to black instead of the default gray but I want to keep all other colors the same as default. When I change Text color to black, the Color Set field goes to Custom and when I save and go to homepage all colors are gone and everything is white. I tried clicking all the padlocks locked on all colors except Text color hoping that would work but the same thing happened. How do I change text color but keep all other default colors?

Also, what is the Alignment Color Scheme? How do the padlock symbols next to each color work? The documentation does not explain any of this.

Thank you, Hank