Alanin blue

Aniline Blue WS, also called aniline blue, China blue or soluble blue, is a mixture of methyl blue and water blue. It can also be one of them. It is a soluble dye used as a biological stain, in fluorescence microscopy, which appears a yellow-green color after excitation with violet light. It is a mixture of triphenyl rosaniline and diphenyl rosaniline trisulfonates.

Aniline blue or its constituents are used to stain collagen, as the fiber is stained in Masson's trichrome, as well as to reveal callous structures in plant tissues.

It can be used in Mallory's connective tissue stain and Gömöri's trichrome stain. It is used in differential staining.