Is there a certain system behind these numbers? I don't get the numbering system!???

Now we have 01 blue, 02 red, 52 blue and also a 52 red??

And someone says, the Chinese serial systems is weird?!

I wouldn't be surprised if they were completely random. A fun mathy anecdote - in WW2, the Allies tried badly to figure out how many tanks the Germans produced. Thankfully, the ever pedantic Germans assigned sequential serial numbers to their tanks. This allowed Allied statisticians, by observing the number of distinct serial numbers encountered, as well as the maximum serial number, to estimate the number of tanks built.

One simple way to check the probability of N tanks being built, given that they've encountered K tanks, with the max number being M, is the number of ways one can pick K-1 tanks from M-1 numbers (since the maximum M is known) divided by number of ways of picking K tanks from the hypothetical maximum, N.

Here's a more detailed writeup on the subject:

https://en.wikipedia.org/wiki/German_tank_problem
So I wouldn't be surprised if random serial numbers were the standard for military equipment.