Why the color variations?

[gnubler]

And it always seems to be oranges or greens, which are the worst colours for CYMK printers to try and match!

In my experience blues are the hardest to match running CMYK.

 

[BigNate]

... once you get a perfect match for the customer - but inside the shop. What happens when they take the sample outside? we have had some inks that look identical under artificial lights, but in the sun were dramatically different.

 

[damonCA21]

In my experience blues are the hardest to match running CMYK.

I have never really had a problem with matching blues, greens tend to be the one that are most annoying for me

 

[BigNate]

I have never really had a problem with matching blues, greens tend to be the one that are most annoying for me

Any mix that calls for Reflex Blue will be problematic on a process color press (unless one of the press's inks is Reflex Blue - never heard of this though...) Some colors just cannot be reproduced with a color gamut limited by primary inks (it does not matter which or how many primaries you use - they just get you closer, but not a full spectrum.)