men in black - Change in neuralyzer color in MIB films

• In Men in Black (1997), the neuralyzer devices employ a red flash.


• A few years later, in Men in Black II (2002), the neuralyzers have apparently been upgraded or modified, and now use a blue flash.


• In Men in Black III (2012), a 1969-time-travel scene shows a young Agent K using a neuralyzer powered by a belt-mounted battery pack.

Agent K originally retired at the end of Men in Black, during the age of red neuralyzers. Yet at the end of Men in Black II, K is shown activating a blue neuralyzer located in the torch of the Statue of Liberty, using his watch.

The implication seems very strong that this neuralyzer was K's secret, as it is activated by a watch which he kept in the locker, with the key hidden across town.

So how could the Statue's neuralyzer be blue? Wouldn't it be red, as that was the last "version" of neuralyzer he used before retiring in 1997?