Ha!, half us wearers complain the hair is too shiny and half of us complain its too dull!

They tend to start off shiny when they're new, but obviously the hair isn't being fed any natural oils or supplements, so it dulls over time.

Using small amounts of product in the hair can maintain or restore the shine.
Even something simple like brylcreme can achieve that.
But its wise to never over do it because too much product can have a negative effect on the look and oils that get down to the base can weaken the attachment.

What I also think you're referring to is is the 'tone' that hair can take on in different lighting conditions.
Ideally, the factory will have matched your hair sample and the replacement hair will reflect light the same tone as your natural hair does.
But in many cases it doesn't always work out like that.

Again, using hair grooming products can help because they 'mask' the hair and then it all reacts the same way in lighting.
But you can also use products like colour conditioners that will maintain the overall colour, but unify the tone.