I swear the button used to light up in Red color. In retail copy all those years back. But now it doesn't anymore, any my minions keep dying out there :(

GoG version, with Unofficial Patch and World Domination Starter Kit installed here.

Any help ? Thanks kindly.

Firstly, I'm pretty sure it only lights up when your minions are attacked - so if it lights up it means you've probably lost some minions. This can happen due to FOJs being there, but it can also happen if a mission is in progress (even without any FOJs in the region). Also you don't necessarily get "attacked" as soon as FOJs appear - sometimes it'll be a little while before you see the effects.

Secondly, although it might be technically "red", I tend to perceive it more as a brief orange flicker, lasting typically less than a second. I've often missed it myself, so I just got into the habit of checking the world domination screen every now and then - especially when there's a mission on-going.

BTW I do have the old CDROM retail copy, although it does have the latest patches (including the unofficial one), so I'd be surprised if it's different.