What grapes can be used for both red and white wine and what are
unsuitable...
(because of insipid flavour resulting or other reasons)

--
J.P. in London.

AFAIK there are no off flavors associated with fermented red grapes off
the skins. As far as insipid flavors well that is up to the palate of
the taster.

Any grape can be made into a white (or blush) wine. The darker the
berry, the darker and fuller the wine no matter how you ferment it. If
you are the type of person that likes white zinfandels or white merlots
then go ahead and ferment some of the stronger red (or blue or black)
grapes off of their skins. If you find those insipid, then you better
stick with the thin skinned red grapes, like pinot noir or pinot gris,
which will give you much more delicate whites.