In the recorded message this week, I mentioned the free newsletter Seeing Color. This note is to make the link to it available. If you subscribe, it will come in email each month.
I also mentioned the Journal of John Woolman. The text is freely downloadable or can be read online. Some may find the older style of his writing difficult. There is also a free audiobook version available on Librivox. You can read from a browser or get the Librivox app for your phone. There are updated and edited versions for sale in all the usual places.