Trouble setting RGBA to node

I’m trying to set an RGBA to a Rectangle node but it’s coming up with the error: Error: in set_fills: Expected "fills.[0].color" to have type {r: number, g: number, b: number} but got additional property "a"

I’m setting it like this
darkFrame.fills = [{ type: "SOLID", color: token.dark.rgba }];

I’ve been reading through the docs and can’t see anything about setting a layout to RGBA values.

Any help would be appreciated thanks

In summary, you need to use color: RGB, opacity: value.