Most Ipe objects can have two different colors, one for the
boundary and one for the interior of the object. The Postscript terms
stroke and fill are used to denote these two colors. They
can be selected independently by clicking with the left or middle
mouse button on one of the little colored boxes in the Color field of
the Ipe window. The currently selected colors are indicated here
as well. You can also set stroke and fill to be empty by
clicking the box labeled empty
. A stroke color of empty
means that no outline of the object is drawn, a fill color of empty
means that no interior will be drawn. Setting both colors to
empty will render an object invisible.
The GL version of Ipe relies on a graphics library that cannot properly handle non-simple filled polygons. Therefore, if you fill a non-simple polygon, it may be shown unfilled or incorrectly filled on the screen. If that happens to you, use the previewer to see how it looks filled. The same can happen for filled polygons with more than a certain number of vertices. (If you run the GL-version of Ipe on an Indigo workstation, for instance, even polygons with more than 256 vertices will not be shown filled. Switch to the pure X-version if this bothers you.)
Imagine preparing a drawing by hand, using a pen and black ink. What Ipe draws in its stroke color is what you would stroke in black ink with your pen. Probably you would not use your pen to fill objects, but you would use a brush, and maybe even a different kind of paint like water color. Well, the fill color is Ipe's "brush".
This explains why text objects, mark objects, and arrows only use the stroke color, even for the filled marks (discs and squares) and filled arrows. You would also use a pen for these details, not the brush (unless you draw very large marks--in which case you probably meant to draw a filled circle anyway).
An interesting exception to the above rules are lines with arrows. If a line with an arrow has stroke color empty, the arrow will be drawn with the fill color, and the line will not be drawn at all. This is useful to create arrowheads without body, which can be used to be attached to objects that cannot have arrows.
The default color panel of Ipe contains some shades of gray and some primary colors. However, you can change these to your own liking in your X resources.