Use the extends attribute to extend one tokens
bundle from another.
To add tokens from one bundle to another, extend the
“child” tokens bundle from the “parent” tokens, like
this.
<aura:tokens extends="yourNamespace:parentTokens">
<!-- additional tokens here -->
</aura:tokens>
Overriding tokens values works mostly as you’d expect: tokens in a child tokens bundle override
tokens with the same name from a parent bundle. The exception is if you’re using standard tokens.
You can’t override standard tokens in Lightning Experience or Salesforce1.