How do I make sure that my blues do not print purple?
When using a blue in your design, always make sure to leave at least a 30% difference in your Cyan and Magenta values.
Take the following example p[rintong 100% of both cyan and magenta. CMYK = 100/100/0/0, or otherwise represented as C: 100 M: 100 Y:0 K:0
While the color on your screen will look blue, it will print purple.
Blue is very close to purple in the CMYK spectrum. Please remember to use a low amount of magenta whenever using high amounts of cyan to avoid inadvertently producing purple colors.
A good CMYK example to get you a nice true blue would be : CMYK = 100/70/0/0, or otherwise represented as C: 100 M: 70 Y:0 K:0