Metamerism is a phenomenon that occurs when two colors appear to be the same under one lighting condition, but not when viewed in others

Why does this happen?  This can occur if the same design is printed on two different printers using different inks.  The reflective qualities of the inks may not be the same, so they will look the same / correct viewed under the light they were profiled at, but different in other lights.  It can also occur on the same printer type if the colours are made in a different way, for example if one printer was making a grey with CMY and the other just using the black ink, the reflective quality will again be different.  The issue will more noticeable when colouring pail neutral colours.

What can you do in AVA to reduce this effect? To a large extent Metamerism is something that happens and you may simply need to accept this in many circumstances.  If you are digitally printing and you have control over the linearization you may be able to reduce the effect.  If you use less if the colours that cause more Metamerism and use the black ink to make grey more than CMY you will reduce the effect.