From what I understand, for non-exempt products, it is per color, per batch. So if you buy two cans of 'crimson' paint, and they are different 'lot' numbers, they BOTH need to be tested... as written now. But read this article on the storque:
http://www.etsy.com/storque/craftivism/cpsia-overcoming-obstacles-and-fighting-for-change-5350/It looks like they MAY be changing the language to make component testing approved, "If as the CPSC has alluded to, component testing is allowed in the near future, items like Heather Flottman’s buttons will be tested by the manufacturer, and it will be affordable and easy for crafters to use them. "
-Quoted from the Storque article linked above.