It helps to draw your lineart first and then either fill in the spaces with color, or to lower the opacity of the lineart and then add color. In order for it to seem that your colors are not mashing together, people would use lineart to separate things, right? Well, when you take out your lineart, you just use contrast of shading and lighting to separate everything.
In actuality, the lineart is "gone" but the shading and lighting makes up for it and, to me, would technically be your new lineart. ^^