When coloring over grayscale you are using the gray as your guide. Where there are dark grays you use dark colors, where there are light grays you use your light colors. Then seamlessly blend your lights and darks together with medium colors. Derwent Inktense pencils work nicely for this style of coloring (provided the paper can handle it) because you can apply your color and then blend it all so nicely together when you activate the pencils with your watercolor brush.
Specific techniques used in the following time-lapse video:
Mediums used in the following time-lapse video:
Another example of watercolor pencils used to color grayscale
I'm a Mom of 2 from Vancouver, Canada. I recently discovered grayscale coloring and loved it so much I published Beautiful Creatures and Beautiful Nature because there were no high quality grayscale coloring books to be found. Join me as I write about the grayscale coloring techniques I have learned and that I am continuing to discover!