Creative Image Editing in Photoshop - Black and White in Photoshop CS4 and Photoshop Lightroom - page 240

Also using a Color Balance adjustment layer, try emulating the
Van Dyke Brown tone, sepia tone and cyanotype print.
The cyanotype print was created by an iron salt sensitizer which
could be exposed in sunlight and developed in water. Cyanotype
prints are characterized by a very moody dark, deep blue tonality.
For the image below, I set the midtone Color Levels input values
to 60, 0, 96.