Plenty excellent Colombian panaderias in Queens - Sunnyside, Woodside, Jax Hts, Corona, etc - but do not know of a spot in Bklyn. If you take the G to 65th & Bwy or 74th and wander along Roosevelt you will see a wealth of places for pastries of all kinds, arepas, chorizo, batidos, etc. I personally favor the one on Woodside Ave just E of 58th (Rico Pan?).
do you mean guava pastries? is the bread sweet? if so, you could try La Flor bakery on 41st and 5th in sunset park. they make several kinds of guava things.
if it's something specifically columbian, then you might be out of luck as i don't know of a columbian place in brooklyn.