One of the basic things that most art programs teach is how to draw shapes.
The reason for this, from a painting perspective, is that even a slight discrepancy in the size of each shape can potentially affect the psychological message of your painting.
Let’s say you make a half-inch wide brushstroke that’s an inch long and it’s yellow. But what if that shape was twice as wide? The chances that it would be more visible, attract more attention, and change the message to make yellow more prominent are overwhelming.
But what if that stroke was only an eighth of an inch wide because your drawing was off, and you needed a certain amount of yellow for the sun, and your stroke was too small and it didn’t feel warm and sunny?
This also applies to value. If you have a light scene and some of your shapes are shaded dark and they’re too big, it could change the percentages of shapes that are dark, and they could overwhelm the lighter ones, changing your whole meaning.
If your shape was a little more diagonal, which signifies recession and action, it could create a psychological effect. If your shapes are parallel to the plane, that’s known as plain and calm, rest, and gives an uplifting sense of permanence. So anywhere in between horizontal to the page and diagonal can affect the message psychologically, and you have to choose how much of a diagonal or horizontal.
Of course, other factors come in, like the intensity and brightness of a color, which we would call saturation, as well as the contrast it’s creating. By the way, you can have the most beautiful portrait palette, but if you don’t have the shapes of the shadows, highlights, and sections on that face spot on perfect, it will never look like that person.