A trichrome stain can colour the muscle tissue red, and the collagen fibres green or blue.
It helps in identifying increases in collagenous tissue (i.e., fibrotic changes) such as in liver cirrhosis and distinguishing tumours arising from muscle cells and fibroblasts.
[citation needed] Usually a red dye in dilute acetic acid is applied first to overstain all components.
It is usually applied from a saturated solution in 80% ethanol and often in conjunction with picric acid (itself a dye) and a polyacid.
The methods exploit minor differences in tissue reaction to dyes, density, accessibility and so on.
In "yellowsolve" methods, a red dye in dilute acetic acid is first applied, then the section is very thoroughly dehydrated to ensure that no moisture remains.