The issue isn't so much with specific colours, but with colour contrast ratios.
WCAG guideline 1.4.3 Contrast (Minimum):
1.4.3 Contrast (Minimum): The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following: (Level AA)
Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.
Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.
At the end of the day you can have whatever colour combination you want. Heck, you can have light-grey on white if you want. It's not exactly illegal. But if it fails WCAG colour contrast guidelines then your site won't be accessible and you're shutting out many users of your website. This'll lose you potential sales, will potentially damage your reputation, and even open you up to lawsuits because you're preventing some people from accessing your content.
Perhaps your blue combination is accessible. You don't state the hexcodes for them so we can't be sure. It's unlikely to be AAA compliant (that requires 7:1 contrast), but could possibly be AA compliant.
There are various colour contrast checkers out there, such as the popular Snook.ca one, so run the colours through there and see what comes out.
Also, accessibility site webaim.org discuss blue colourblindness. Blues are the least effected colours for colorblind people - red/green is far more common, however there are people with blue deficiencies:
Tritanopia (blue deficiencies)
Tritanopia is much less common than the other categories mentioned above. Tritanopia is the insensitivity to short wavelengths (the blues). In general blues and greens can be confused, but yellows are also affected in that they can seem to disappear or appear as lighter shades of red.
However just because people can't determine blue so well doesn't mean your content is going to be inaccessible to them, providing the contrast is OK and it's still readable. It just won't look blue to some people.