Are the same bricks in different colors more expensive to manufacture?

Why does LEGO do this? I’m disassembling my Voltron to put it away, and I noticed that some pieces hidden deep inside the build are completely different colors than the surrounding bricks. Once the model is fully assembled, nobody can even see them. For example, in this section they used a pink piece and a turquoise piece instead of yellow like everything around them. Why not just keep all the hidden pieces the same color? Is there a reason LEGO does this, or is it just whatever parts they...