Melissa,
Normal museum lighting for pastels is a fairly dark room. That is the context of the information on the Rembrandt Pastels web site. Test them yourself by putting sample swatches on a pastel board and place them in a window in direct sun, with half of each swatch covered by a black mask. Check them every few days, comparing the covered half with the exposed half. It's a simple enough thing to do, and it will clear up all the confusion, and you won't have to rely on what anyone else has said. Do it with every color you're considering using, and then decide which ones to use after they've been in the sun for a year.
Virgil Elliott
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