The most common protein staining methods include: silver stain, coomassie blue staining, and fluorescent stains. 

Coomassie Blue

The two main types of coomassie blue staining are colloidal Coomasie and classical Coomassie. 

1. Colloidal Coomassie protein staining offers a balanced approach between traditional Coomassie staining and silver staining. It exhibits excellent sensitivity, is easy to use, and works well with protein mass spectrometry. 
2. In the classical Coomassie protein staining method, gels are soaked in a Coomassie staining solution that colors the whole gel, not just the proteins.

Silver Stain

Silver staining utilizes proteins' ability to bind silver cations (Ag+). The silver cations attach to the proteins and are then converted into metallic silver by a developing solution, resulting in an image. 

Fluorescent Stain

Fluorescent stains are ideal protein stains as they provide high sensitivity, have an easy protocol, a broad dynamic range and have compatibility with mass spectrometry. However, they are generally more costly than Coomassie or silver staining methods and need specialized equipment.