Comment by chris_st

There's a book where the author tested watercolors which my watercolor teacher said was extremely controversial when it came out, but she was able to replicate some of his results, and so changed which colors she bought.

I tried the colors she recommended, and got good results. I also tested various black pens, and found (25 years ago!) that Micron pens were colorfast. Some black (gel, IIRC) pens faded to a nice sepia.