There isn't one specific dye used for all microscope slides. The choice of dye depends on the type of sample being viewed and the specific features that need to be highlighted.

Here are some common dyes used in microscopy:

* Methylene blue: A basic dye that stains nucleic acids, cytoplasm, and some bacteria.

* Crystal violet: A basic dye used for Gram staining to differentiate between bacteria.

* Safranin: A basic dye used in Gram staining as a counterstain.

* Eosin: An acidic dye that stains cytoplasm and extracellular structures.

* Hematoxylin: A basic dye that stains nuclei and other acidic structures.

* Sudan black: A dye used to stain lipids.

* Acridine orange: A fluorescent dye that stains nucleic acids.

Therefore, the "name" of the dye is dependent on the specific application and the type of microscopy being performed.