In the '50's the U.S. went nuts with nuclear weapons tests

doogievlg said

This video blew my mind the first time I saw it.

Click to expand...

I did not notice different colors in other countries.
But USA had blue and purple.
Anyone know what do the purple ones in the USA mean?
The first I notice are around 5 mins in 1964.
I see some too in 1973.
And more in the 80s.