If colors are electromagnetic waves, and electromagnetic waves are electric and magnetic fields, how can we see colors at the same time? Looking around thru space we see a variety of colors. If colors are simply electromagnetic waves and waves are just forces then why don't these electromagnetic waves of each colors cancel or add up to each other and why can we still distinguish individually among the electromagnetic waves of each color and produce a different color?
 A: 
How can we see colours at the same time ?

I am going to assume your question is about the mechanics of human vision. We can see in colour because there are several different types of light sensitive cells in the retina at the back of the human eye. Colour vision comes from cone cells. There are three types of cone cells - one type reacts most strongly to photons of red light, a second type is most sensitive to green light, and a third to blue light. In addition we have rod cells, which are very sensitive to photons across a range of wavelengths, and allow us to see in light that is too dim to trigger the less sensitive cone cells. All of these cells (there are millions of each type in a human retina) produce nerve impulses and the brain does some very complex processing of these nerve impulses to produce what we perceive as colour vision.
This Wikipedia article explains in more detail how these different types of light sensitive cells work.
A: Light is a ray photon particle whose energy is given by
$$E=h\nu$$
Light corresponds to different colors are different energy photons.

why don't these electromagnetic waves of each color cancel or add up to each other.

Photon particles can not be added nor they can cancel each other. When the two photons see each other inside the LHC, they sometimes overreact with excitement and split themselves into an electron and positron pair. These electron-positron pairs are not fully formed entities, but rather unstable quantum fluctuations that scientists call virtual particles.
In phenomena, like interference, it seems waves interfere constructively or destructively, but actually it's a wave function that interferes.Here

how can we see colors at the same time?

Photons of different energies reach our eyes at different points and thus We able see them. More on this here.
