Color field is missing from properties when contour is included in selection set
Typically, when a selection set includes various kinds of entities, their common features are visible in properties. When a contour is part of a selection set that also includes non-contours, then the color property isn’t available in properties.

Exhibit A - Selection set of several types of entities.

Exhibit B - Contour added to selection set.
Workarounds: Use the properties toolbar
First Appeared: Land Desktop 2006
Status as of 2008: Still reproducible
Status as of 2009: (unknown)