Ask Mr. Smarty Plants

Silver, maybe? Black? Turquoise? It depends on how narrowly you want to define the term. See this previous answer on most common color in which one of our Mr. Smarty Plants team speculates on how you would narrow down which color is which, and points out that there is no answer to that question because no one has surveyed the whole world and catalogued all the colors by frequency of appearance. It's on our to-do list, but we may not get to it this year.

We also wish to submit that there is a color that is no color, because these plants do not bloom. They do not need colored flowers to attract pollinators because they do not reproduce that way. Some examples of that type of plant are:

Ferns - reproducing by spores, small brown spots on the underside of the fern leaf. From backyardnature.net Backyard Ferns. From our database Adiantum capillus-veneris (common maidenhair)

Horsetail - From our own Native Plant Database, Equisetum hyemale (scouringrush horsetail)

Conifers - Backyardnature.net Conifers. Also from our database: Taxodium distichum (bald cypress)

So, have we wandered about enough to divert you from the fact that we can't answer your question? It's hard for us to admit this, but it does happen. Perhaps you would like to take on the cataloguing of all the earth's flower colors, and then we'll know the answer.

Equisetum hyemale

Taxodium distichum

Adiantum capillus-veneris