Legal analysis: You can sign the contract with a blue ballpoint pen, which is generally no problem, but it is recommended to use a black or blue pen. There is no rigid requirement for the color of the pen when signing the contract. It's valid as long as I sign it myself. What kind of signature is used does not affect the legal effect of the contract. Generally, a black signature pen is used, and the handwriting is not easy to fade for a long time.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 143 A civil juristic act that meets the following conditions is valid:

(1) The actor has corresponding capacity for civil conduct;

(2) the meaning is true;

(three) does not violate the mandatory provisions of laws and administrative regulations, and does not violate public order and good customs.