Paint to Compare
Selected
objects can be painted with any of four different colors by pressing the desired color swatch button in the
toolbar:

The paint remains until it is either overpainted with a different color, or all the coloring is reset by pressing the "Reset Colors" button in the toolbar.
Because of its permanent nature, painting is well suited for comparing objects: paint a few objects with one color and then use a different color to paint the objects that you want to compare.
