Again, printers do not mix-up colors, it’s your eye who did it. Looking under the Printer’s Loupe, you see that individual colors (CMYK) are knitted very close to each other and are interpreted by our eyes as different color combinations.
We can do a mile-long discussion about color, for now that’s it. Don’t overwhelm yourself with too many technicalities yet.
To wrap up, there are two media that are prevalent in the world today – the virtual media, the ones we see on our mobile phones, TVs, computer monitors and other media screens – they use Additive Colors (RGB). While those we see on palpable printed materials such as brochures, magazines, billboards use Subtractive Colors (CMYK).