Well, all I can say is that all the blues look very similar in tone, but not exact matches. The earphones have a matte metallic royal blue tone, and the cable looks like a normal sky blue, if but a little darker than usual. The case itself looks like the same but darker tone of blue as the earphones. 

At a cursory glance, though, it's difficult to see these distinctions and really only becomes fully evident when enlarging the images. (It wouldn't be important to me, mind you, and I can't really see what the big deal is...but then I can't really decide what's important for other people. :8} )

In terms of how to respond to the customer, all I'd ever do is say 'sorry you were disappointed with the item' then provide any and every option I'm prepared to offer in order to resolve, which relies on their reply and choice to action. Most people respond and choose an option, some might say what about xxx and if I think it's acceptable, I'll agree, a few never replied at all, they just want the complaint heard, I guess.

My best suggestion, if indeed it applies ?, is to have something in the description along the lines of 'hand selected components in blue tones".