The internet provides open access to a tremendous amount of information, including peer reviewed, scholarly material. However, be mindful of your sources. Consider the following:
Authority - Who is the author? What is their point of view?
Purpose - Why was the source created?
Publication & Format - Where was it published?
Relevance - How is it relevant to your research?
Date of Publication - When was it written?
Documentation - What sources did they cite?
Below are reputable websites written by authorities in their subjects and provided for the improvement of public knowledge.
Coloro Workspace - The Coloro Workspace is a revolutionary digital tool designed with, and for, creative professionals to explore and work with color in a digital space. All 3,500 colors in the Coloro system are available in Coloro Workspace, allowing you to play with them in different ways.
Forbes Pigment Collection - This overview of the pigment collection held at the Harvard Art Museum provides brief clips of the curator explaining how various pigments have been made historically.
CCA Materials Library - From California College of the Arts, this site catalogs the school's material collection. Each entry includes image(s), manufacturer information, and a list of material attributes.
Fisher Fine Arts Library Material Collection - This extensive collection of material samples from the University of Pennsylvania features images in the public domain as well as object attributes and manufacturers.