The Color Wheel
COMPLEMENTARY COLORS
* Complements are the opposite colors on the color wheel.
* Try a complementary color for shading instead of black.
VALUE
Light
Dark
Tone --- Add white
Shade --- add complement or black.
UNDERPAINTING
--- a sketch of color so that the white
canvas/paper is not so intimidating.
(It can even be done with a rag
--- just cover the surface.)

UNITIY
For UNITY in a painting, use what is
left on your brush somewhere
on an opposite area
of your canvas.
Some palettes to consider :
Example