Off Topic flashes (need help)

[Chigi]

Hi, guys. I need your help
Please tell me how to make it so that you can only turn on the blue flasher on the car so that it flashes? And only from the next stage to be blue with red (this is realistic, as in life in Ukraine). I would be grateful for your help, here is a link to my topic, everything is described in detail there on lspdfr -

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[Chigi]

I know that this requires a script, but what exactly and how it is called - I have no idea