Colin Kaepernick In Top Secret Harlem Photo Shoot

Colin Kaepernick surfaced in the streets of Harlem on Friday -- rockin' a dashiki and posing with a diverse group of young people ... and TMZ Sports has the video.

It was all for a photo shoot that the people behind the production didn't want you to see -- despite the fact it all took place on a public street in the middle of the day.

Unclear what the big secret is ... but there were people on set with GQ promo materials.

Kaep has been spending time in Harlem lately -- he recently donated $25k to the local DREAM Charter School as part of his $1 million pledge.