This article pertains to prints printed via CMYK color mode, which includes most printing of small cards, midsize prints, small posters, and outdoor media.
In photoshop and Illustrator, you can pick colors and view the CMYK color values.
When using blue in your design, always leave at least a 30% difference in your Cyan and Magenta values.
EXAMPLE: C 100% M 10% Y 0% K – This will appear cyan.
Blue is close to purple in the CMYK spectrum. Remember, use a low amount of magenta whenever using high amounts of cyan to avoid purple.
EXAMPLE: C-100 M-70 Y-0 K-0 – If the percentage difference between C and M is less than 30%, the blue will begin to appear purple once printed. This second example will likely still appear blue in your final prints since the percentage difference is 30%.
EXAMPLE: C-90 M-80 Y-0 K-0 – This mix may appear purple on your final prints. You can see that the value difference between C and M is only 10%.