Objects: outline and fill
Although we get a little ahead of the subject of how to apply color in our illustrations (which will be seen in detail later) it is important to point out one very important fact: objects have border color and fill color. In the lower bar we can apply colors to our objects. Having selected one, we click on the chosen color and it is applied to the object; if we click the color with the shift key held down on the keyboard, the color is applied to the outline.
The most advanced fill and contour options are in the dialog on the right "Fill and border", which we can also get from the top menu Object> Fill and border.
Rectangle with yellow fill and red border.