Awhile back I decided I would see what would happen if I pushed a roll of Portra 400 to 3200 and a roll of Fuji Superia 800 to 3200. I took shots from low light and indoor daylight as well as almost no light. Here's what I found. Pushing both films resulted in very red hues and a lot more grain. The contrast is super high because you're actually taking in a lot less light to properly expose and the processing(chemicals) are pulling out the image. I actually really liked the grain that I got from the Fuji 800 but the grain from the Portra was less than desirable since it's such a fine grain to begin with. Here's just a few shots from the rolls and not many turned out the way I had expected. I love the learning process with film though. It's therapeutic for me to be making photos and learning the process along the way.
These photos are from the roll of Portra 400 pushed to 3200. Not a lot of keepers in this roll, but I was "pushing" through the roll knowing full well that this was an experiment.
These images were from the Fuji Superia 800 roll pushed to 3200.