- any of the `147 named CSS colors`_, e.g ``'green'``, ``'indigo'``
- an RGB(A) hex value, e.g., ``'#FF0000'``, ``'#44444444'``
- a 3-tuple of integers *(r,g,b)* between 0 and 255
- a 4-tuple of *(r,g,b,a)* where *r*, *g*, *b* are integers between 0 and 255 and *a* is a floating point value between 0 and 1

.. _147 named CSS colors: http://www.w3schools.com/colors/colors_names.asp
