  21st Century citizens are faced with the need to remember numbers of PINs
(Personal Identification Numbers) in order to do their daily business, and they
often have difficulties due to human memory limitations. One way of helping
them could be by providing cues during the PIN entry process. The provision of
cues that would only be helpful to the PIN owner is challenging because the cue
should only make sense to the legitimate user, and not to a random observer. In
this paper we report on an empirical study where we added colour to the PINpad
to provide an implicit memory cue to PINpad users. We compared the impact of
colour PINpads as opposed to grey ones. As expected, the ability to recall a
PIN deteriorated significantly over time irrespective of the type of PINpad
used. However, there was ultimately no improvement in the ability to recall
PINs when using colour PINpads.
