I have a small program that I use (not ACT) that allows me to add a custom color field to any event. Therefore, when I create a calendar, I can color different events (personal, work, church, school) and then have them show with a color or background when I print/view the calendar. It is a really handy way to separate events. MS Outlook has a category field which allows you to color different activities as well.
Sometimes when I make a call, I am not making it for work but for my family or my church, etc. It would be huge if ACT could distinguish these.
ACT has no way to do that other than to use the TYPE field to separate these types of events (that is, add Personal, Church, School to Call, Todo in the Type list) You can create a category field for a contact (ID/Status) but there is not such field for Activities.