Most people start with their logo, and choose primary and secondary colour schemes from it. If you already have a logo, this process is quite simple. Each colour has its own “hexadecimal code” to identify it, such as #cccccc – grey, #fff – white, or #000000 – black. Use the colour picker and create a file where you can record your primary and secondary colour hexadecimal codes.
This will help you stay consistent when setting up your font colours or block background colours, etc. For the RGB (Red Green Blue colour model for displaying colours on a computer screen) equivalent, see https://www.colorcodehex.com/ .