What realm does a promise `onResolve` belong to?

promise-realm-check.js

var red = $262.createRealm().global;
var blue = $262.createRealm().global;
var yellow = $262.createRealm().global;
var purple = $262.createRealm().global;
var thenResult = {};
var finallyResult = {};

var who = new Map();
who.set(red.Function, "red");
who.set(blue.Function, "blue");
who.set(yellow.Function, "yellow");
who.set(purple.Function, "purple");
who.set(Function, "self");

var blueThenFactory = blue.eval(
  `(result) => (onThen, onCatch) => { result.onThen = onThen; result.onCatch = onCatch; }`
);

var purpleOnResolveBlueThenable = purple.eval(
  `(then) => () => ({ then: then })`
)(blueThenFactory(thenResult));
var redPromise = red.Promise.resolve();
yellow.Promise.prototype.then.call(redPromise, purpleOnResolveBlueThenable);

var blueThenable = { then: blueThenFactory(finallyResult) };
var purpleOnFinally = purple.eval(`() => {}`);
yellow.Promise.prototype.finally.call(blueThenable, purpleOnFinally);

print(who.size);
Promise.resolve()
  .then(() => {})
  .then(() => {
    print(
      "then",
      who.get(thenResult.onThen.constructor),
      who.get(thenResult.onCatch.constructor)
    );
    print(
      "finally",
      who.get(finallyResult.onThen.constructor),
      who.get(finallyResult.onCatch.constructor)
    );
  });

result.log

#### engine262
5
then red red
finally yellow yellow

#### JavaScriptCore
5
then red red
finally yellow yellow

#### Moddable XS
1
then self self
finally self self

#### SpiderMonkey
5
then blue blue
finally yellow yellow

#### V8
5
then blue blue
finally yellow yellow