No. 0 (so-called Colorless Blender) is a clear, alcohol-based solvent which can be used for a variety of purposes such as fading/blending colors, pre-soaking paper, or adding highlights into areas that are already colored. Also No. 0 is great for fixing the coloring mistakes and it pushes the quality of your artwork.

Applying No. 0 in advance

If you want the whole area to be lighter, then try pre-soaking your paper with No. 0. First, apply No. 0 onto the area you want to fade.
While No. 0 is still wet, apply the color you want to fade over the top.