A couple comments on items raised by mindless1 above. In general I did not have those bad experiences with my Lexmark.
Both on my Lexmark and on my current Brother the drivers provided allow you to specify whether or not you are printing in colour. If you are, all three colour toners MAY be used; it not, only Black is used. This choice s NOT set on the printer, you must use the printing options available within the document's Printing menus, and the choice cannot be made permanent. The automatic default setting is to use all colours. In the case of my current Brother system, there is a very handy system in the printing options configuration screens to prepare and store named sets of printer options for different types of jobs. So for example I have created profiles combining choices for Letter and Legal size papers with B/W or full colour and with one- or two-sided printing. Then there's one for B/W only Envelope printing using the single-sheet feeder tray. For EVERY print job I automatically go to the options screen and pick the profile I want to use. If I'm printing several different pages it keeps the Profile I chose between jobs until I choose another. This is much handier that the older Lexmark system, but even with that I could do such custom printer settings.
With any printer the ink or toner of a particular colour normally is NOT used if that colour is not what you are printing in that spot. In a laser printer each of the four colours (Cyan, Magenta, Yellow and Black or CMYK) has its own separate imaging drum. As that drum turns during printing it is first charged up electrostatically and evenly, then the light source (laser or LED in Brother's case) hits the drum and removes the charge in the lit-up spots, leaving an electrostatic pattern of the spots that are supposed to be printed in that colour. Then it runs past a closely-spaced (but not touching) second drum coated uniformly with toner dust and the dust is attracted to the imaging drum to create the exact toner pattern. Where the printing drum does NOT have a charge, NO toner is taken from the toner drum. The imaging drum then contacts the sheet of paper to transfer the toner dust to the paper surface. This is done for all four toner colour units in rapid sequence during the single pass of the paper past the units so that ALL toner is now on the paper surface. The last step it to pass that paper under an intense heat source that melts the adhesive polymer coating on the toner particle surfaces so they all bond tightly to the paper. In this system, toner is consumed ONLY in the spots where it IS going to be transferred to the paper as part of the image. Ideally all of that will end up on the printed sheet. However, a small amount of toner can fail to be transferred, so at the end of the cycle the imaging drum is brushed clean of any leftovers so they don't accumulate and mar the next print.
The details of a file to be printed can impact its use of toners in a colour printer. Even if it consists only of black text on a white background, if that file really is encoded as a "grey-scale" document, the colour co-ordinates of all of the text contain values for each of the four toner colours. Even the darkest "grey" that looks black MAY call for some toner "colour" which you never actually see on the print, but is may use toner anyway. If you set the printer options to print in Black and White only, no matter what the data from the computer tells it, the PRINTER will ignore the three colour signals and use NO toner from those three units, printing only from the Black unit. That is how you can guarantee NOT using toner on a B/W document that needs no colour anywhere.
In the simplest cheapest ink jet printers there are three colour inks only (Cyan, Magenta and Yellow) and NO Black ink. In that case the only way to produce blacks (for text or anything else) is to print LOTS of ALL three colour inks to make really dark grey. In a better ink jet you get a fourth ink colour (Black) and its driver should offer the choice to print Black only when you wish. Colour laser printers are never made with that simpler 3-colours-only design.
The impact of using colour toner on cost is twofold, and I tracked my toner use and costs with my former Lexmark unit. First, although the cost of a colour toner cartridge was similar to that of a Black cart, the Black cart normally contained TWICE as much toner, so the cost per print is different. THEN add in that a Black-only print will use toner from only one cartrige (but maybe a lot for a full sheet of text), whereas a full-colour print may use toner from FOUR cartidges - how much of each depends entirely on how much area of the print uses which colour. Over the longer term with my habit of using Black only on text-only documents, I found that full-colour prints cost about four times (or a bit more) as much as black text pages. Bear in mind that my colour prints often were full sheets of colour like photographs or signs.
Regarding colour fidelity and the cost impacts, I found a supplier of third-party toner cartridges for my Lexmark that produced coloured prints with very good colour accuracy and proper saturation. The difference using those carts versus genuine Lexmarks was very small and acceptable to me. But I DID pay attention to that, to cartdridge print yield and to operatring problems as I evaluated some third-party carts at first because those CAN be sources of trouble. (In contrast, for the dedicated Epson 4" x 6" snapshot photo printer I use, I have found the best performance and print quality there when using only genuine Epson carts for it.)
Last comment on this. I have used HP colour inkjets for many years because they always do well and produce great prints. I got away from those mostly because of the clogged jet issue which is NOT an HP problem. It is largely because I don't use the printer very often, and often in black only. But I still have a couple of those for large colour photos use mainly, and one I use for long banners, but they are old and malfunctioning at times. I did have on old HP Laserjet Black-only printer from the early 1990's that i really liked and used for a LONG time with great success. When it started to fail - poor paper feeding becasue of old dried-out rollers - I decided to get a COLOUR laser, and that's when the Lexmark was chosen. So I have no experience with Colour Laser printers from HP.