Components cannot use hues outside defined color palette

Use Case:
I want to use {{#paper-toolbar}} with the color blue-grey with a hue of 200.

Actual Case:
Color options must be within the default color palette ($primary, $accent, etc) and cannot be overridden with a hue on a per-component level.

Expected Case:
Something such as

$header: "blue-grey";
$color-blue-grey: map-merge($color-blue-grey, ('default': '200'));
{{#paper-toolbar header=true}}

Or some other way to define custom colors for specific components.

If there is a way to do this, the documentation needs to be update because it is not clear how to do it.