The colour that your wooden floor will end up is hugely dependent upon the age of the floorboards / wooden floor and an indication of this is by the width of the planks. Narrower boards of, say, 5 inches are comparatively newer than wider floorboards and, therefore, lighter when varnished and the older floor boards of, say, 6-8 inches and over, are generally older and, therefore, darker when varnished, even with a clear varnish. This refers more to pine, which is the most common form of wood used as floor boards in houses across the UK . Of course, in instances where you have oak or mahogany etc., then your boards will turn out according to the relevant type of wood. Coloured varnishes are definitely not recommended.
Should you wish to darken your floors then you will have to have a floor staining process and we will advise you on your specific requirements. Please be aware not to go too dark in colour, as the only way to go lighter afterwards is to re-sand, attracting additional cost to yourself. Also, please note, that a stain is only a representation of the chosen colour, be it oak or mahogany etc. For example, you cannot CHANGE your pine floorboards to oak floorboards merely by staining the floor boards. You would need to have oak floor boards fitted, to have the floor boards look EXACTLY the way oak looks. Stains are, in the most, not opaque, the stains have transparency and with that, the grain and even a representation of the original colour of the wood is likely to show through.
In instances where liming or whitening is desired, it is advised to be very careful. Some home renovation/interior design magazines illustrate these types of floors as part of room sets. In most cases, these floors have been laid specifically for these room sets, using new or hand picked floorboards. They are subjected to various photographic re-touching techniques and have been optimised by use of photographic lighting effects etc. In most real cases, floorboards are not as perfect as this and, therefore, do not turn out as refined as this.