If youre getting a focused beam at 5-6000ft its a very powerful l@ser.
If I could possibly add my 2 penny worth having worked on l@sers since 1978.
To get a focused beam at 5000 - 6000 ft would also take some pretty complex optics and high powers,in most part out of reach of normal Joe Bloggs.
Blue l@sers do exist and in fact were one of the first gas l@sers,these are extensively used in the entertainment industry where they then filter out the blue component to give green light.
These blue l@sers are Argon l@sers with a fairly wide beamwidth of 488 - 518 nM.
Since working on l@sers in the military,medical and now industrial fields,I have never condoned their use in confined places e.g. discos etc, as although the blink reflex will in most cases protect the eye there are too many variables to make this theory usable.
As stated before there are rules and regulations in the use of l@sers and these should be adhered to at all times.
Unfortunately since the advent of e-bay etc there are a lot of old medical and scientific systems available to people who would think it great fun to make your plane glow on it's approach.
This should be stopped before an accident happens and the only way do this is to get HSE informed.