Using colors

We can add colors as options to \draw, as we did for Figure 2.3 when we added blue lines. When we look at circles, ellipses, and rectangles, we can see that the element can have one color while the inner area can have another color. We can add the latter using the fill option.

It’s easier to see it with an example – to draw a blue circle filled with yellow. For this, we can write the following:

\draw[blue,fill=yellow] (0,0) circle [radius=2];

Let’s now fill colors in Figure 2.9. We’ll use fill=yellow for the circle, fill=black for the ellipses, and make the arc thicker by using very thick. Also, let’s omit the rectangle. Our commands are as follows, in a complete document, with the changes highlighted:

\documentclass[tikz,border=10pt]{standalone}
\begin{document}
\begin{tikzpicture}
  \draw[fill=yellow] (0,0) circle [radius=2];
  \draw[fill=black] (-0.5,0.5,0)
    ellipse [x radius=0.2, y radius=0.4];
  \draw[fill=black] (0.5,0.5,0)
    ellipse [x radius=0.2, y radius=0.4];
  \draw[very thick] (-1,-1) arc [start angle=185,
    end angle=355, x radius=1, y radius=0.5];
\end{tikzpicture}
\end{document}

When we compile this document, we get the following:

Figure 2.10 – A smiley with color

TikZ has another way of filling called shading. Instead of filling with a uniform color, shading fills an area with a smooth transition between colors. For our smiley, we chose a predefined ball shading that gives a three-dimensional impression. We set the shading=ball and ball color=yellow options for the face, and ball color=black for the eyes. The code becomes the following:

\draw[shading=ball, ball color=yellow] (0,0)
  circle [radius=2];
\draw[shading=ball, ball color=black] (-0.5,0.5,0)
  ellipse [x radius=0.2, y radius=0.4];
\draw[shading=ball, ball color=black] (0.5,0.5,0)
  ellipse [x radius=0.2, y radius=0.4];
\draw[very thick] (-1,-1) arc [start angle=185,
  end angle=355, x radius=1, y radius=0.5];

Now, our four draw commands produce an even fancier smiley:

Figure 2.11 – A smiley with a three-dimensional appearance

In Chapter 7, Filling, Clipping, and Shading, we will learn more about choosing and mixing colors and explore various ways of filling areas with colors.