Are all the photos of the universe really so colorful or is it just visual effects that are added later? Do the colorful pictures of the universe show how it looks like that in reality or is it just a visual effect that is added later.
There is no straight yes or no answer. 

Some objects do have significant radiation in visible part of the spectrum which would make them colorful if we would be close enough while observing them (our eye needs large number of photons to distinguish color so that means, astronomy wise, that object needs to be either very bright or very close or both).

On the other hand lot of them are being adjusted for color later. Usually most beautiful images are mosaics of several images from different filters (even from parts of spectrum our eye cant see) where each image is given a specific color based on filter used and then later all of them get combined.

If you want to learn more check this very helpful paper, which has some tutorials as well:

http://www.stsci.edu/stsci/resources/imaging/papers/rector2007/files/Rector2005.pdf

Btw, as a curiosity - images from rovers on Mars are mainly black and white and are colorized later (thats why the rovers usually have a color wheel on them for calibration purposes as seen here). This lead to uncertainties of color of Mars sky which turned into a long lasting debate.