Mandala example (radial symmetry)

You have to draw a circle with compass and divide it on 8 or more equal parts.
You already know how to divide a circle on 12 equal parts.
Here is the tutorial: How to divide a circle into 8 equal parts

Let's say that this is your color sketch; mark with a pencil the repeating part – the module:
Make a circle on a Bristol paper (leave at least 1/2 inches at the left and right) and divide it on needed amount of parts (in this case 12)

On the Bristol paper draw thoroughly 1/12th part that you marked on your sketch

Accurately trace it onto a tracing paper

Note: you can use a usual paper, further working with the light box or a window.

Flip the tracing paper, put it on the next section of the circle on Bristol paper, and accurately trace over the lines, pressing with medium hardness. When you remove tracing paper, you will see a pencil imprint of the second part; then you should draw over it, clarifying the lines.

Note: if you use the light table, place the tracing (or a usual) paper under the Bristol paper and trace directly onto the Bristol paper.
If you have a furniture with a glass shelf, you can make a lightbox yourself. Just be careful

Now you have two mirrored parts

Optional: at this point you can add the second, mirrored part, onto the tracing paper, and then trace the mandala parts only 5 more times instead of 10.

Proceed tracing the pattern parts until you finish the design

Erase the extra lines. Your mandala is ready to be colored.