[SalesForce] How to use a JavaScript object as an aura:attribute

You can set a the value of a Lookup field with the Id of the record it references.

For example, if you have a Contact object you can specify a default for the Account lookup, by specifying an Id string for the AccountId field.

<aura:attribute name="newContact" type="Contact"
    default="{ 'sobjectType': 'Contact',
               'LastName': 'Smith',
               'AccountId': '001i000002zxpz1' 
             }"/>

You could also leave it blank and then set it in your JavaScript before calling to your Apex controller.

<aura:attribute name="newContact" type="Contact"
    default="{ 'sobjectType': 'Contact',
               'LastName': 'Smith',
               'AccountId': '' 
             }"/>

And, prior to enqueueing the action set the value explicitly.

var con = component.get("v.newContact");
con.AccountId = '001i000002zxpz1';
action.setParams({
    con: con
});

Or, you could leave it blank altogether and set it in your Apex controller:

@AuraEnabled
public static Contact createContact(Contact con) {
    con.AccountId = '001i000002zxpz1';
    insert con;

    return con;
}

The problem is XML does not allow the use of unescaped < or > characters. In Apex (which is where Lightning Components gets its type system) arrays and lists are equivalent. We typically use array notation in attribute defs because you do not have to < and > encode the []. Try this instead:

<aura:attribute name="colorPalette" type="docSampleNamespace.Color[]"/>