>In the case of Latin viridis, the most closely related IE root is
*w(e)ra:d-
Reconsider. Latin has vireo, to be green or to be vigorous. It is a
typical -eo stative verb, with the typical deverbative noun form viror.
Why is this not the base root you are looking for? Pokorny 1133 *weis
"sprout, grow" explains this fully and adequately.
Typically there is an adjective in -idus associated with these
statives/deverbatives. It is worth noting that in this case we get viridis
instead of the expected *viridus, but I don't think we should abandon the
etymology on that basis.
Peter