Legal analysis: there is no hard and fast rule on the color of seal oil for effective official seal. But the general administrative seal is the red official seal, and the business seal is the blue official seal. The provisions of the official seal are as follows: the official seals of state-owned enterprises and state-owned joint-stock enterprises (including company seals and department seals) are all circular, with a diameter of 4.2c, a five-pointed star in the center, a star tip diameter of 1.4c, and a circular edge width of 0. 12c. The names of foreign publications of the five-pointed star circulate from left to right, or the front of the name circulates from left to right, and the back circulates from left to right. The seal specifications of departments under collective ownership and individual and private enterprises are circular, with a diameter of 3.8c and a width of 0.1c. The five-pointed star is published in the central journal, and the name of the enterprise approved in the business license is printed on the seal, circulating from left to right, and the printed words are simplified Chinese characters. Special business seals are all round with a blank center, with a diameter of 4.0c and a width of 0.1c. The arc above is the unit name, which circulates from left to right. The contents of the special seal are placed horizontally at the bottom of the seal, and the simplified font is used for printing.

Legal basis: Article 490 of the General Principles of the Civil Law states that if the parties conclude a contract in the form of a contract, the contract is established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.

A contract shall be concluded in written form as stipulated by laws, administrative regulations or agreed by the parties. If the parties do not do this in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.