I agree with everything you said in your article. I would also like to add one more source:
A color wheel. One of those round (paper) wheels that show the colors and then the different shades of each color. Also they usually have some explanation about complimentary, analogous or tertiary colors, etc. Usually these can be found in the art department with the paints and brushes. It can be very helpful once you figure out how to "roll the wheel."
You also mentioned that many companies sell their products in groupings (coordinating colors, coordinating papers, embellishments, etc). Sometimes these companies also sell a color coach that helps customers explore color combinations. This information might also be available online somewhere within each company's website.
Just thought I'd bring this up.