In the dozens of motorcycles that I have worked on, I have never seen a paint code anywhere on the motorcycle itself. While newer cars generally have a sticker that says exactly what the paint code is on it, motorcycles do not have this.
So where can you actually find the paint code? Finding the paint code for your motorcycle can be much harder than on a car. Even slight differences in the paint can result in a very different overall appearance. Likewise, if you are repainting your motorcycle entirely and want to preserve the original color, you likely will not be happy with the results of just buying a paint that seems to be close to what you need. That way, if you wanted to just repaint one section of your bike or touch up one part, you do not have to worry about the paints being slightly different colors. These allow for you to know exactly what color of paint that you need to exactly match your stock paint. Each manufacturer comes up with their own unique paints that they sometimes use across all models, a single motorcycle, or several models. If you are wanting to exactly match the paint that is on your motorcycle, it will be extremely difficult to find a paint that matches from just searching through general shades of grey.