With most modern printers you use what's known as "CMYK", which means you have a cartridge for Cyan (a light blue), Magenta (pink), Yellow (Yellow), Key (black). When you print red, the printer basically spits ink from each cartridge on top of itself to convert it to the other colors. Red is a maximum usage of yellow and a maximum usage of magenta on top of each other. Since you only end up with yellow, that means your magenta line is either clogged, empty, etc.
Things to try:
Printers generally have a head cleaning utility, as well as a "nozzle check". Head cleaning will drain ink from all the cartridges to try to clear clogs. Try doing a head clean once or twice, then do a nozzle check, the nozzle check should have all the aforementioned colors on it (yellow is sometimes hard to see). Most printers print out a dashed line, if your magenta starts coming out and is missing a few dashes, another cleaning should resolve it. If after 3 cleans it still isn't pulling any magenta, I'd consult Epson, or look into how to do a more thorough cleaning on the printer.