I DO remember seeing a map where the text of varying thickness or darkness was used to create a map/image...but I can not remember where or what. I am not sure that would suffice for your project as they might not be able to distinguish the changes in the text. You might want to find out just WHAT impairments you are to make allowances for.
If you want to convey terrain by touch, I believe that there are papers and inks that can be used to layer an image with each layer having a certain noticeable thickness to it. Again going from (faulty) memory here....better to ask Gameprinter about that. And the last method that I can think of is 3D printing.....used in some industries like Architecture and Model creation.
As for the colors...I wouldn't think that using too much shading would be a good idea....use mostly solids and none too similar to another...
Hope that helps some