if you are into financial forecasting or product marketing analysis, where you would be needing graphs and charts, then buy a colour jet.
else, I would blindly recommend a laser jet (mono). the laser (however will be expensive, but prices have come down drastically as i bought a mono HP and i was sitting in a PC store yesterday and saw a Samsung colour laser for same price. and imagine how i felt
. the yield of laser jet is very high. plus the print quality is very precise in terms of fonts and line drawings.
keep in mind, if you intend to use letter head, and your letter heads have plastic coating or some logo with plastic paint. then using laser jet wont be good, as the paper rolls over a heated roll. so it will stick to the roller. also, i have seen some companies with rough surface paper letter pads (high quality paper, but not smooth). this will as well wont be good for a laser jet.
the colour jets, eats up your ink in 300 papers (max), while laser jet will give you some near about 2500+ (depending on the printer brand and cartridge model). so make your mind before buying, anymore confusion, either add here or pvt msg me. your spelling of color tells you're from UK, are you?