Lexmark x2670 wont print colour red

put paper in the cartridges and insert them

Black is not a color by itself. It is the presence of all colors making it black. White is an absence of all color making it white. Now you need a new BLACK Cartridge,

Make sure the magenta cartridge is not empty.
If it's not, then try the print head cleaning function in the printer utility window. In "Devices and Printers" select the printer in question to get the window

Just make sure you are inserting genuine Lexmark cartridges. Lexmark does not recommend the use of refilled, remanufactured or clone cartridges, you might not get the print quality you expect from ink that is specially formulated by Lexmark.
Try cleaning the cartridge nozzles using the Lexmark software installed on your computer instead:1. On your computer, go to Start menu.2. Go to Programs.3. Go to Lexmark 2600 Series folder.4. Select Lexmark Solution Center.5. From the Maintenance tab, select Clean to fix horizontal streaks. Your printer will then print a page forcing ink through the cartridge nozzles and clean it from dirt and possible clogs.
Should the problem continue, please contact Lexmark Technical Support Center to have your genuine cartridge replaced. They might ask for your receipt so have them ready. If you're not using genuine supplies, please replace your cartridges with original supplies.

Just make sure you are inserting genuine Lexmark cartridges. Lexmark does not recommend the use of refilled, remanufactured or clone cartridges, you might not get the print quality you expect from ink that is specially formulated by Lexmark.

Try cleaning the cartridge nozzles using the Lexmark software installed on your computer instead:
1. On your computer, go to Start menu.2. Go to Programs.3. Go to Lexmark 2600 Series folder.4. Select Lexmark Solution Center.5. From the Maintenance tab, select Clean to fix horizontal streaks. Your printer will then print a page forcing ink through the cartridge nozzles and clean it from dirt and possible clogs.
If that doesn't help but you're using genuine Lexmark supplies, please contact Lexmark Technical Support for additional assistance, otherwise, please replace your color cartridge with a genuine one.

Try to insert a different known working black cartridge to identify if it's a faulty cartridge issue.

Try to reseat the black cartridge. If that doesn't help, try to clean the cartridge nozzles. On the printer operator panel > press Setup button > Maintenance > Clean Cartridges > Ok. Your printer will then print a page, forcing ink through the nozzles to clean them. Try to print again. You may also try to insert a different known working black cartridge to determine if the other is faulty. If your new cartridge is faulty, return it to the purchase store (if within return period) or contact Lexmark technical support for assistance.

What are the versions of your cartridges inserted in the printer? Open the printer cover and remove both cartridges. Close the cover. Unplug and replug the printer into the power outlet in the wall to reset it. When the printer turns on, reinsert both cartridges and make sure they are properly inserted. Check for any errors. If error continues, please contact Lexmark technical support for additional assistance.

Your colour ink cartridge may need to be replaced.

All the best!
damnor01

Just read this document:

http://www.lexmark.com/publications/pdfs/2007/2600/v7649663_en.pdf