Blue clay is generally used for the storage and numbering of internal documents and internal data (to distinguish it from red clay).
Red clay is generally used for bills issued to external parties (not easy to fade).
Official seals are generally red
Signatures are generally blue
Enterprises and institutions generally use red ink ink, and blue ink ink is rarely used. However, it is mostly used by foreign trade enterprises or foreign capital. They usually have square seals and need to be covered with blue ink. Foreigners do not recognize red sealant paste, thinking that it contains azo and is easily carcinogenic to the body. In ancient Chinese calligraphy, blue ink paste is generally used during mourning!
Please accept it if it helps, thank you.