Yes it will print green. The machine doesn't really "sense" what exact color of ink is inside the cartridge, but some can read the sensor and see if it is the right catridge, however that means nothing if you put a different color in it yourself. It counts on the user to fill them and insert them correctly. It can sense the amount of ink left, however :)
Toner costs much more per purchase than inkjet ink, but each cartridge lasts much longer so per page they are considerably cheaper. Some cheap lasers aimed at the home market do not work out as cheap (sometimes noticeably more expensive than other lasers) per page, but will still beat a 'jet in the long run.
If you do very little printing, then the inkjet will win overall but if you do a moderate amount or more even a cheap laser will work out cheaper in the long run. But if you only do a little printing there is another noticeable factor against inkjets - they tend to gum up if left alone for a couple of weeks so you end us wasting half your ink doing head cleans next time you use it - bringing the cost per page up higher. My last Epson was terrible for this, and it wasn't a cheap grotty model either.
On good photo paper a good inkjet will produce better photo results than a cheap or mid-range laser, often better than an expensive model. But that again brings up the cost considerably, and on normal paper (standard 80gsm/90gsm stock) all but the cheapest lasers will win out these days. And if you plan to print much plain text (letters, documents) again the laser wins (you don't want to use good photo paper to get crisp text from an inkjet when you can get the same text quality on standard stock out of the laser.
There is also the problem of speed. Never trust an inkjet's claimed speed. My last one claimed "up to 20 pages/min" but it couldn't even pass blank paper through at that rate, and its highest speed setting wasn't worth bothering with. That lovely full page photo could take a number of minutes to create - my laser will kick its version out in seconds. I would doubt the pages-per-cart claims of inkjets too, especially for colour output as nth figures are based on colour text not blocks of colour like a chart or photo, much more so than lasers which in my experience get much closer to their rated output per cart.
These days I go with a colour laser, my current one is a Xerox 6125 which I got a good offer on last year (lower price and free toner carts, which brought the effective price below the cheaper units I was considering) and have been very happy with it, and if I want a few more professional quality photo prints I take the files to Boots or Tesco and use their facilities or self-serve printing machines. What I used to do was to have a B/W laser for docs/letters/draft and a colour inkjet for anything that absolutely required colour.
Don't get the cheapest colour lasers as they sometimes have noticeable banding issues in colour output and once you tot up all the consumables (check how long the drums last before needing to be replaced as well as the toner) don't work out a lot cheaper than jets. If you can get print samples of plain text and business graphic (text with relatively flat colour like charts and such) and photo output for any model you consider just to be sure. My Xerox 6125 has decidedly better photo output than my brother's Samsung 310 (though the Samsung's photo output isn't terrible, its basic colour output fine, and b/w output no worse than the Xerox).
Two other points to consider: a laser will be much quieter, but most colour lasers are significantly larger and need more space around them for ventilation.
Best Answer
Very unlikely unless you're keeping the toner in an especially warm and humid location.
I purchased a Samsung Laser MFD (CLX-6260FW) over two years ago, and I've had no issues with it. It came with a set of "starter" toner cartridges:
About 1.5 years after receiving it, the cartridges each showed as "0% remaining" and required "immediate user intervention" so I purchased more to be prepared (6k Black, 3.5k CMY), but a further ~7 months later, the original cartridges are still going strong. Others have suggested that toner can still be good after ten or more years.
Toner cartridges can benefit from a gentle shake (side-to-side), which helps to redistribute the contents, but this tends to be required when they start to get low and show print issues... rather than due to toner clumping up. Be wary of vigorous shaking, as any toner leaks / spills will be a significant issue (for both cleaning and respiration).
I flat out refused to buy a printer for a long time, but it's become more necessary for me in recent years. I decided against any inkjet technology (including HP PageWide / fixed head printers, which can be presented similarly to a consumer) for a number of reasons... critically:
With the price and size of laser printers now, I'd recommend that nobody purchases an Inkjet ever again (budget permitting of course, they are still a bit more expensive in the short term).
While laser printers are quantitatively worse for high-quality photo printing, I'd suggest that unless high-quality photo printing is a very important and regular use-case for you, laser will be just fine. For occasional high-quality photo printing, use an online service.
To expand on the running costs of an Inkjet printer briefly, consider some random HP cartridges.
While the upfront cost is much higher, the running cost is significantly lower (probably better than ~50%).
HP Inkjet Black Ink Cartridge
An approximate ~5.5p / page of black and white only printing... completely ignoring the use for alignment, head cleaning, wastage due to being dried out, wastage due to re-prints, wastage due to DRM, etc...
High capacity inkjet cartridges (e.g: HP 973X) can work out dramatically cheaper than this on a strict per-page calculation, though their high-capacity nature will incur a far higher cost due to wastage for infrequent printing.
HP Laser Black Toner Cartridge
An approximate ~2.4p / page of black and white only printing.