Aldrich lists trypan blue as a suspect carcinogen. It is a vital dye, and is often used in that fashion. It can be used to demonstrate amyloid in a manner similar to that of congo red.
R. D. Lillie.
Conn's Biological Stains
Williams & Wilkins, Baltimore, MD., U.S.A.
Aldrich chemical catalogue, 1992
Aldrich Chemical Company, Milwaukee, WI, USA.
Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.