... might be old news, but I just noticed that Vallejo has posted an Equivalency Chart that allows you to cross reference their Game Color line with Rackham, Citadel and Reaper Master Series paints and even notes which are perfect matches and which are close matches.
There is also an Equivalency Chart for the Model Color line with Federal Standard, RLM, Ral, Tamiya, Humbrol, Gunze, Revell, Testors, Andrea, Film Color and Rackham.
An invalulable reference if you ever need to cross reference colors between manufacturers.