Calculating background color’s complementary red, green, and blue colors

I am not new to UI design, but I have absolutely no experience with color schemes.

Say I choose rgb(35, 51, 72) as the base and background color. This is #233348 and hsl(214, 35%, 21%). Are there methods of calculating a red, green, and blue that go with that base color?

Take https://demo.vaadin.com/lumo-editor/ for example. There are a few dark presets available. Is it possible that every color is derived from the base color? If so, how? I guess my question is, how does one derive all of the color choices on that page from the base color?