For longevity, you must use a concrete stain to apply color to the counter top. This usually involves acid to etch the surface followed by the stain color. It is a fairly straight forward process that can be accomplished by most DIY-ers with moderate skill levels.
The problem that you should consider pertains to health issues. This staining process is used mostly for floors not kitchen surfaces where food is prepared. There is a possibility that once the stain has been applied it (ie any chemicals in the stain) may be transferred to any food placed on the counter.
Some manufacturer's state their stain is "bio-friendly" which sounds safe, but on closer inspection of the warning label it also claims "not safe in food preparation areas". Not all stains will be unsafe. Here is one link to such a product hat uses etching.
Also take note that wear and tear will make it necessary to re-finish the surface over time. Try to find a product that is the most simple to get the color you desire, will endure in it's environment and is safe to use.