Typescript: dynamically calculated field on object initialization

Question

I'm building a design system in Typescript and I would like to have fields for lighter/darker color to be calculated dynamically based on the main (required) color. The setup is following:

export default class Color {
  main: string = "#000000"; //required color
  light?: string = calculateLight(this.main);
  dark?: string = calculateDark(this.main);
}

Color object is then used in Palette type:

type ColorTypes = "primary" | "accent"; //I need this to restrict available values later in components' props

type Palette = {
  [key in ColorTypes]: Color; //created based on ColorTypes for easier code updates
};
export default Palette;

Now i would like to initialize Theme using Palette with curly braces:

export const theme: ITheme = {
  palette: {
    primary: {
      main: "#323130",
    },
    accent: {
      main: "#0078d4",
    },
  }
};

But light and dark fields remain undefined.

Is there any way to have it done automatically? Or the only way to do it is using a helper function like createTheme which would iterate through each Color in Palette and execute a constructor or function?