For many years the ACT! Calendar & Task List has linked color selection with priority. This inhibits the ability to assign color independent of of priority to satisfy a need for associating color to a particular user and activity. In working with users, I find that intutively people would like to quickly and visually identify their own or their workgroup's activity in the clutter of a calendar. While you can filter by user in a calendar to mask other users entries it is not as helpful as the natural visual filter that the eye can make to discern colors amongst clutter.
A frustrating side effect of the current color/priority association is the pre-loading of the Activity Schedule form with the color of the prior selected activities priority. For example if I have assigned a priority and hence a color to a Meeting activity for myself and another combination for a Call activity, the last color scheduled wins in the creation of the next activity, irrespective of the desired color association for the newly selected Activity type... So then there is the need to select the correct color for the activity. This in turn preloads the Activity Schedule form for the next time it is used. A continuous sequence of unnecessary re-assigning of color to the desired user choice is set off.
An extension of that finer control over these attributes would be the ability to sort by color in a Task List view. This would effectively provide the ability in a single column header click, sort by two attributes, User and Activity Type....a productive, low-click count feature.