You may want to try using the colr.org API: http://www.colr.org/api.html http://www.colr.org/api.html The entire colr.org dataset isn't available, but you can

You may want to try using the colr.org API: http://www.colr.org/api.html http://www.colr.org/api.html The entire colr.org dataset isn't available, but you can make ajax requests for individual hex values, typically in less than 100ms. The dataset should also include the standard CSS and HTML color names. This was part of the initial buildout several years ago.