Luxol fast blue is commonly used to observe myelin under light microscopy. It is the alcohol soluble counterpart of the water soluble; Alcian Blue. The stain works via an acid-base reaction with the base of the lipoprotein in myelin replacing the base of the dye and causing a colour change. Under the stain;

Myelin fibres appear blue,
Neurophil appears pink,
Nerve cells appear purple.

References

Sheehan D, Hrapchak B, Theory and practice of Histotechnology, 2nd ed,1980, pp262-264, Battelle Press, Ohio