Colouring
There are many ways to dye or stain wood, Mike has used and tried most methods, spirit based dye's give the best results if your after natural even colouring, standard off the shelf dye's can be intermixed, darkened, warmed or lightened, but for deep colours such as wenge or black i prefer to use powdered dyes mixed with metholated spirit, unlike off the shelf stains, spirit powder dyes can achieve very deep colourings. Dye's can be over coated with any Oil modified, waterbased varnish or Hardwax 
Tinting is another way to colour wood floors, you may just want to warm an existing colour or age the flooring, tinting done right can achieve this. Certain woods such as maple and some poor grades of beech do not stain well, so tinting of these types is sometimes the only option 
Colour washing is ouralternative to bleach, unlike bleach, colour washing does not damage the wood. Light subtle washes can be achieved in almost any colour as well as opaque pastel colourings. Colour washing is most effective on light species of soft and hardwood such as pine, ash, beech and oak.