“Most celebrities and athletes are taught not to do blue ink cause you can scan and forge the signature on other things and sell them,” wrote one user. Another added “for computer scanning ...

Scientists at the Institute of Nano Science and Technology (INST) have developed a groundbreaking luminescent ink with advanced security features to combat counterfeiting in currency, certificates, ...

the brown ink is made of a mixture of the red, blue and yellow inks. This is because the spots in the brown ink are at the same heights (and have the same R f value) as the reference inks.