Oki C5150n is printing only magenta. Very little traces of yellow, blue but no greens at all. Everything else is just magenta!

You either have contaminated developer powder BAD or need to change all 3 colors usually not black, and Developer powders (wor$e) or change your CYAN, YELLOW, MAGENTA toners.( the 3 super secret colors that make up our norm red green blue SSSHHHH don't tell anyone one...even if it's me)

I had the same problem. I came across the 160 error after I moved drums around. My issue started with error code 161. which appears to be the Magenta drum. Moving it to other color locations gave me errors 160, 162, 163. 160, I assume, is the cyan cartridge, then 161 is the magenta, 162 is the yellow, and 163 is the black. In my case, the magenta was very dirty. I pulled it out, used an eraser from a #2 pencil to clean the contacts. Used the shopvac to clean toner power out of printer. Turned it back on and it worked.

It all depends on the meaning of 'not properly'.

Try creating a document with four different squares, or words, of these colours: yellow, magenta, cyan and black. If all of them print (albeit not with the correct shades) it is probably an ICM driver error. But my guess is that only one of those four colors will print badly, due to a defective color cartridge.
The OKI 5150 makes all perceivable colours using cyan, magenta, yellow and black toners, so if one of these malfunctions, the resulting colors will lack the required shade of, say, yellow, and will appear to be "wrong". The yellow colour itself, of course, would simply disappear (the "yellow" you use might actually be 95% yellow and 5% cyan; then the "yellow" square will be printed as a very light shade of cyan, while the other colors - say, 95% magenta and 5% yellow - will turn out almost exact).

Try with the color test and replace any failing cartridge; if all four (almost) pure colours do print incorrectly, it's unlikely to be a cartridge problem, and we'll have to dig deeper.

this printer uses leds to charge drums. if you lift top cover you will see 4 black windows ( 1 above each drum) make sure they do not have toner on them. green usually means you have some toner on the magenta led which causes missing magenta (yellow and blue make green) if it is on black and white prints it could be something else like a pile of toner under transfer belt (which you can pull out, after you take out drums) check the leds first

You need to replace the magenta drum. Just because there is life left; it's possible it is scratched. Also, take a cotton ball dip in alcohol and wipe the LED's off when the cover is open; those black things that are hanging down from the cover. Also, make sure your drums are installed in the proper spots (magenta in magenta slot). If the toner "rubs off" after it prints... then the fuser is defective.

I am presuming the rest of the page prints the correct colour and this is an area in the direction of feed that is missing yellow. Try swapping the yellow and magenta drum positions and then the green text should come out a very dark blue colour. if it does then the fault is with the YELLOW drum, if there is still a noticeable Cyan stripe still then the fault will be with the LED head or engine control board.

You need a new black drum.

Check the LED Head and LED Connection. The LED heads are interchangeable, BLK, Cyan, Magenta, Yellow.

One of the drum cartridges is stuck. Test by removing them one at a time with the printer off, then turning on.

First, clean the LED heads with a lint free cloth and isopropyl alcohol (the LED heads are the attachments on the underside of the lid when you open your printer; four of them for each color). Try printing something after doing that. If it's still an issue just with black, try switching the black and magenta drums/toner (keeping them locked together). The drum w/ toner cartridge simply pulls straight up and out, no switches or locks to flip. Then print a page of text; which will output from the printer in magenta. If that looks okay, then it may be an issue with your black drum and needs to be replaced.