How can it be Turing-complete with only two colors and one state? I thought you needed at least two colors and three states to be Turing-complete. https://en.wikipedia.org/wiki/Wolfram%27s_2-state_3-symbol_T...
EDIT: Also, as the article that you link points out, while all definitions of Turing machines agree on their power as a class, minimality results like this are quite sensitive to the details of the definition. (In particular, the article seems to hedge its bets by saying that that machine may be the smallest universal machine.)
That's mostly just my intuition though; it is very possible that I am wrong.
(There's a textbook example where you can add auxiliary memory to a (1D) Turing machine, called a "multi-tape" Turing machine. And you can reduce that to a single-tape Turing machine, but at the cost of blowing up the number of states in the finite automaton).