To best advise, it would be helpful to be able to see what you are seeing. 
Could you please send us photos of the situation?
Up to three at a time can be attached directly to this reply.
We'll be happy to take a look and give you our thoughts.


Christine

Thank you for the photos. This looks like moss (though the residue in the third photo is harder to ID, but might be tiny clumps of moss). Moss plants have no true roots, so should scrape off fairly easily. There are a select few herbicides that target moss specifically (other herbicides will not), though their use should not be necessary; their ingredients may consist of a type of metal sulfate compound or potassium salts of fatty acids. The moss is not harmful and fine to leave alone as-is, unless you are concerned about safety (trip or slip hazard when wet). Mosses require a certain amount of moisture to thrive (or at least to establish), so perhaps the soil under those pavers isn't draining as well as would be needed to discourage moss growth.

Miri