You could have found it in the wiki:
http://www.amsn-project.net/wiki/index.php/Frequently_Asked_Questions#In_the_preferences.27_privacy_tab.2C_what_do_the_different_colors_in_the_contacts_mean.3FQ: In the preferences' privacy tab, what do the different colors in the contacts mean?
A: You should notice the colors in the list headers:
Allow List: Green foregound
Block List: Red foregound
Forward List: Red background
Reverse List: Yellow background
A contact in any list will take a different color depending the lists that contact is contained on:
1. If it's in Allow list, it will have green foreground.
2. If it's in Block list, it will have red foreground.
3. If it's in Forward and Reverse lists, it will have white foreground.
4. If it's in Forward list, but not in Reverse list, it will have red foregound.
5. If it's in Reverse list, but not in Forward list, it will have yellow foregound.
6. If it's not in Forward or Reverse list, it will have a black foreground.
Let's be a bit more specific:
AL : Contacts in this list always have a green foreground. If a contact has a yellow background, it means it's in your reverse list, but not in your contact list. If the contact has a red background, it's in your Forward List (so, you have it), but not in the Reverse List (he or she doesn't have you). If the contact is both in Reverse and Forward list (a standard contact), the color is white (standard). Finally, if the contact is not in your Forward List, and not in the Reverse List, the contact background is black. You can safely delete this contact from the Allow List, as you don't have that contact in your contact list, and he or she does't have you!
BL : Exactly the same behavior as Allow List (AL), but in Block List contacts always have a red foreground.
FL : Foreground will depend on the contact being on AL (green) or BL (red). White background if the contact is in Reverse List too, Red background if the contact is not in Reverse list (he or she deleted you). In last case, the contact will have the special icon img/wiki_up//notinlist.png in the contact list.
RL : Foreground will depend on the contact being on AL (green) or BL (red). White background if the contact is in Forward List too, Yellow background if the contact is not in Forward list (you have deleted it).
