I found an article in Popular Science Magazine (see link below) which gives a general overview of different stains that can be used in microscopy. The article divides the stains into three categories:

• Common household chemicals: this includes Iodine, for example. They are very readily available.
• Substances used mostly for microscopy: Methylene blue, Hematoxyline, and Eosine belong to this group.
• Commercial substances: they are sold by companies specializing in microscopic chemicals.

The article also provides a step-by-step guide on how to stain a blood sample (don’t do this in schools due to danger of infection).

Link to the article: Help Your Microscope with Stains and Reagents (Popular Science, March 1937)