Apologies if this is common knowledge, but I didn’t know this.
As the title says, I just did this last night and was able to unlock the special red camo by doing all the guns classes even tho the event is over. If you don’t remember what the challenges were for each gun class, you can find the camo in every gun class under events in the camo section. Or you could check here too – [https://dotesports.com/call-of-duty/news/all-diabolical-camo-challenges-for-the-boys-event-in-mw2-season-4-reloaded](https://dotesports.com/call-of-duty/news/all-diabolical-camo-challenges-for-the-boys-event-in-mw2-season-4-reloaded)