What is the tail in SolidPaint's boundVariables.color.id

I am develop a plugin that can apply variable colors by some rule.
I found I need to assign the value like this:

I am using

const tokensCollection = libraryVariableCollections.find(collection => collection.name === "Tokens");
  if (tokensCollection) {
    const libraryVariables = await figma.teamLibrary.getVariablesInLibraryCollectionAsync(tokensCollection.key);

    const hoverlibraryVariable = libraryVariables.find(variable => variable.name.includes("Hover"));
    console.log(hoverlibraryVariable.key)
}

but it only get “e1b04111db373f08ec909607224cbaf0ff8aa032” part