An old USN-issue sewking kit:
Note the colors of the threads: Navy blue, white and khaki. Those were enough to mend all of the uniforms that were worn back in the day.
I don't know if the Navy still issues sewing kits and if there are threads compatible with the new camo uniforms or the now-discontinued aquaflage.
As to why a sea-based service needs to wear camouflage uniforms, well, I've blogged about that.
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