No, you can use various colors according to your fingerprints. There is no specific legal requirement to use inkpad, but you must use special inkpad for stamping, so your handprint is different from the inkpad for stamping.

To affix/print/seal (to ...)

In civil activities, there are countless private seals. Compared with the signature, the legal risk of stamping is great:

First, if the private seal has not been registered by the relevant departments, it will have no credibility.

Second, the private seal is separated from the person, unlike the signature, which is "like a person" because of different personal handwriting, so it is difficult to determine whether the private seal under the cover represents my meaning.

Third, the private seal is easy to forge, so the parties may claim that what the other party says has nothing to do with them.