There is no special requirement for the color of the official seal in mainland law. The general seal shape is not clearly defined, but some special seals are: invoice seal is oval, contract seal and customs declaration seal are mostly oval, official seal is round, and foreign official seals are mostly oval and polygonal. Sometimes for the convenience of work, two similar seals will be distinguished by two or more shapes.
The customs seal is a blue official seal, such as the customs export inspection seal of multinational shipping companies when they go abroad. Maybe it's because red seal is very common in China. But foreign countries do not recognize it. People are all blue. If they are red when you show them the quarantine report, they will think you are copying it. After all, they have never seen red in their own country. As for the business seal, no, but if there is a transnational contract seal signed under the supervision of multinational lawyers, there must be a two-color seal. In this way, whether it is a lawsuit at home or abroad. The contract is established.