Is it possible to serve the military if you are colorblind?

Depends: Pilots, military police special ops, disqualify color blind. Rest of military best to check with local recruiter office, but i don't think it is a problem.

Extent of sxs: "failure to pass a color vision test is not an automatic disqualification. Although there is no standard, color vision will be tested because adequate color vision is a prerequisite for entry into many military specialties." see dod directive 6130.3 & dod instruction 6130.4.

Yes: There are many color blind persons in the military. A few types of military occupations might be forbidden the color blind, but you can serve

Depends on MOS: AR40-501 Ch13-2f: "failure to pass a color vision test is not an automatic disqualification...color vision will be tested because adequate color vision is a prerequisite for entry into many military specialties...for entrance into the USMA, Army ROTC or OCS programs, the inability to distinguish & identify without confusion...a vivid red...or green does not meet the standard."