[Marco B]

Some links to organizations involved in art conservation that you may find useful to explore:

http://www.conservation-us.org/
http://www.cci-icc.gc.ca/index-eng.aspx
http://www.incca.org/
http://www.getty.edu/conservation/
http://www.campbellcenter.org/pages/resources.html

And you may find this page revealing and handy, from the Watercolors page on the Handprint webpage:
Doing your own lightfastness tests

And especially the results of light fastness tests of specific coded pigments as summarized here:
Summary of 100 common pigments: http://www.handprint.com/HP/WCL/palette1.html

and detailed info here:
Detailed summary of 750 pigments: http://www.handprint.com/HP/WCL/waterfs.html

if you think the above test isn't relevant (it's about watercolor paint mainly), than realize that watercolor paints are actually paints without any significant amount of binder like oil, so almost pure pigment. Hence testing watercolor will at least give you a "worst case" result for the stability of the pigment involved and probably faster test results.

Marco