def update_color(self, asset_string, hexcode):
response = self._requester.request(<EOL>'<STR_LIT>',<EOL>'<STR_LIT>'.format(self.id, asset_string),<EOL>hexcode=hexcode<EOL>)<EOL>return response.json()<EOL>
Update a custom color for this user for a given context.

This allows colors for the calendar and elsewhere to be customized on a user basis.

The `asset_string` parameter should be in the format 'context_id', for example 'course_42'.
The `hexcode` parameter need not include the '#'.

:calls: `PUT /api/v1/users/:id/colors/:asset_string \
<https://canvas.instructure.com/doc/api/users.html#method.users.set_custom_color>`_

:param asset_string: The asset to modify the color for.
:type asset_string: str
:param hexcode: The hexcode of the color to use.
:type hexcode: str
:rtype: dict