Munsell color system, 1915, Albert H. Munsell - Pre-Pantone
You'll find a lot of your favorite museums: National Gallery of Art - Musée d'Orsay - The Smithsonian - MoMA and so much more. Check out the The Permanent Collection and Galleries, Exhibitions and Shows Lists too.
You must also view the Virtual Vatican Sistine Chapel. I actually felt as if I was standing in the Chapel once again. Such beauty!
Troll through the online museums for some quick inspiration for your next art work.