“There are fish of every hue.” For different kinds of fish, should fish be in plural form here

Many nouns which are normally uncountable are potentially countable in certain contexts. It’s a matter not so much of grammar as of the nature of the object to which the noun refers. There can clearly be different kinds of foil, and that makes it possible to speak of foils. Matter is a concept that that lends itself less well to pluralisation, but the Corpus of Contemporary American English has this record:

A 1992 study estimated that CSOs release between four and fourteen billion pounds of solids and organic matters on a yearly basis nationwide.

Organic and inorganic matters might in some contexts be an unwise formulation, because it could be taken to mean ‘organic and inorganic topics’.

David Crystal comments on the pluralisation of uncountable nouns in the latest post on his blog.

Deers has been used that way.

From A Popular History of Mammalia, 1850:

The subgenus Muntjacus is distinguished from the other deers by the horns being supported on elongated pedicels ...

From Comparative Genomics, 2000:

In contrast to other deers, the muntjaks display chromosome numbers ranging from the lowest chromosome number known in mammals of 2n=6 (female) and 2n=7 (male Indian muntjak; Muntiacus muntjak vaginalis. Figure 8) to 2n = 46 (Chinese muntjak; Muntiacus reeversi).

I would say that either deers or deer would be acceptable for this type of usage. However, if you want to be indisputably correct, you could use species of deer. I also suspect this is the most common term for this meaning, as neither deer nor deers sounds quite correct to me here.