Getting Started
There are a few ways to address themes and schemes for the web, I'm going to go over using custom properties (css variables).
:root {
/* named colors (personal preference) */
--battleship-gray: #858786;
--celtic-blue: #276fbf;
--eerie-black: #262626;
--folly: #ff495c;
--mint-cream: #f1fffa;
--background: var(--mint-cream);
--on-background: var(--eerie-black);
--branding: var(--celtic-blue);
--on-branding: var(--mint-cream);
--secondary: var(--eerie-black);
--on-secondary: var(--mint-cream);
} Other Approaches
Naming variables things like `primary`, `secondary`, and so on can be another approach. I feel like either makes sense but just stick to something once you've nailed it down.
:root {
--primary: var(--celtic-blue);
--on-primary: var(--mint-cream);
--secondary: var(--mint-cream);
--on-secondary: var(--eerie-black);
--tertiary: var(--eerie-black);
--on-tertiary: var(--mint-cream);
}