Blue and purple are very close in the color spectrum. A CMYK blue set at 100% Cyan and 100% Magenta will look very blue on-screen and appear purple after offset print or digital print.
To resolve this issue, make sure Magenta is 30% less than Cyan when using very high Cyan values.
This will adjust the color further away from the purple tone and should print closer to the desired blue.
We highly suggest designers invest in a Pantone process color guide to get a good starting point to see what their cmyk values will look like printed.
Always trust the values, and not what you see on your screen.