Changing label color vs sprite tint

I noticed that changing the color of a label does not add an additional draw call, while changing a sprite tint does. What is the difference between setting the color of a label and the tint of a sprite? And how does a label change color without generating an additional draw call?

Setting a sprite tint equates to setting a uniform / constant, but a labels color is part of its vertex attribute, meaning you can share the draw state for all labels if you just change the color. A couple of components support custom vertex attributes, meaning you can introduce a sprite color that can batch by yourself: Defold materials manual