Combination of two seemingly different communication strategies.
The nautical flags as a communication method between ships, combined with the undertext of Blue Money (as opposed to Green Money or Black Money), which includes this idea of the money that comes from the sea, which pretty much Greece and Athens is made of.
The apotropaic Medusa head which turns everything into stone, and the legend that it carries.
In other words, Blue Money is a contrast of schemes, of a situation which is embellished communication and another one which is apotropaic, dismissing and turbulent.
It could be described as a Medusa, whose apotropaic stonifying look is the flags of Blue Money.