Blueface 's features may have taken on a purple glow after he let Ryan Garcia punch him ... because he was having some trouble breathing in a wild new vid.

The boxer livestreamed his hang with the rapper Friday night ... and, just 15 minutes into the stream, the duo engaged in an age-old guy tradition -- one dude punching another as hard as possible. Gallery Launch Gallery Getty

Blueface asked if Garcia wanted to throw a haymaker at him ... and Garcia accepted -- though BF wore protective gear over his stomach to lessen the blow.

He also had one request from Garcia ... telling the other man he didn't want to crap his pants since he'd just recently eaten. Getty

The two then lined up across from one another. Blueface pulled up his arms and Garcia uncorked a vicious blow t

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