No need to go anywhere :)

  >> words: keys-of system/words
  >> types: collect [forall words [if datatype! = type? get/any words/1 [keep words/1]]]
  >> probe types
  [datatype! unset! none! logic! block! paren! string! file! url! char! integer! float! word! set-word! lit-word! get-word! refinement! issue! native! action! op! function! path! lit-path! set-path! get-path! routine! bitset! point! object! typeset! error! vector! hash! pair! percent! tuple! map! binary! time! tag! email! handle! image! event!]

Even easier:

  help datatype!

It can't be that easy, or can it? :-)

The Red website has it somewhere, but they're focusing on the Lang and not the site at the moment, so it might be hard to find. I think the Rebol website (successor language that is mostly compatible although interpreted only) should have a lot of those.

> I think the Rebol website (successor language that is mostly compatible although interpreted only) ….

I think that this is backwards; Red is inspired by Rebol, which is relatively old:

> Red is a computer programming language. Red was made to overcome the limitations of the programming language Rebol.

(https://en.wikipedia.org/wiki/Red_(programming_language) ).

here is a list of datatypes from REBOL days, Red is probably mostly there

http://compsci.ca/v3/viewtopic.php?t=17726