The differences between colour and mono (black and white) laser printers is in the toner and drum mechanisms. These printers work by using a laser to create an electrical payment pattern on the drum. This is then used to pick up toner, and roll it over the paper. Where a black and white printer does this once, a colour laser printer will do this once for every colour that's being located on the page, and will interpolate distinct spots of distinct colours of toner to make distinct hues and shades.
What this means is that for a colour laser printer, there's a greater series of expendables to be had - you have to buy anywhere from three additional colours of toner (for Yellow/Magenta/Cyan) to six distinct colours for high end photo-lithographic colour laser printer.
Printers Multi Function
Most of the additional price of colour laser printers has come from the added wear and tear on the drums in the mechanism; the typical laser printer drum in a desktop printer used to be good for about 20,000 impressions before it would get worn to the point where it wouldn't issue toner (this is why worn out drums tend to leave streaks of lighter printing down one side or the middle of a sheet of paper).
Advances in drum technology have increased considerably on the higher end printers - many now have drums that are good for half a million pages or more...however, with colour laser printers having to do a detach pass for each colour laid down, the normal rule of thumb is that a colour drum will last for about a quarter as many printed pages as a black and white printer's drum would.
What these advances in drum endurance mean is that colour laser printers have come to be significantly less high-priced to purchase, and they've commonly come to be cheaper to operate, as the estimate of vendors producing colour toner sets has increased, driving the prices down. As a result, they've moved from 'high end office equipment' to 'most businesses will have one' and are fast production their way down to the consumer end of the market as well.
If you're finding for a colour laser printer, understand that there's a clear demarcation between 'business colour' and 'photographic' or Pantone colour. In an endeavor to support selected pricing on the devices, the manufacturers are adding capabilities, but most of the inexpensive models have relatively unsophisticated colour gamuts, which makes them good for printing, say, letterhead reports or pie charts, but will get noticeable flattening of colour gravidity when used for photographs or similar items where subtle shadings in hue are needed.
That being said, many of them are now at the point where the cost of printing a colour page with modest amounts of coverage (about 15% to 20% of the covering in color) are only two to three times as high-priced as printing a black and white page from a dedicated printer. Even full coverage can be reasonably priced with some of the higher end models.
Differences in the middle of a Mono and Colour Laser Printer