Finnish workshop students toned their cyanotypes as follows:
First, they bleached their prints in used Dektol working strength
solution (almost any alkaline bath works, Crawford recommends a 5%
solution of ammonia), then prints were washed, and toned in Tannic Acid
solution (one spoonful of tannic acid in one liter water, amounts are
not critical), for red-brown tones some used also sodium carbonate
(again one spoonful to one liter) after tannic acid. After toning comes
the final wash. Some of their work can be viewed at URL below.
Hope this helps,
Jalo
http://www2.spt.fi/~porkkala/vvt.html