Primeiramente, eu encontrei "Como sinalizadores de versões anteriores são atualizados para o Outlook 2007" e então Eu encontrei esta pergunta que duplica a sua em techtalkz.com " Exibir as categorias de cores no Outlook 2003 ":
Outlook 2003 Colored Flags were migrated to Color Categories in Outlook 2007. There is no link in how Color Categories in Outlook 2007 are downgraded to Color Flags in Outlook 2003. This would be impossible as well considering the fact that there are many more colors to choose from in Outlook 2007 than in Outlook 2003.
However, the Categories assigned in Outlook 2007 are still assigned in Outlook 2003; they are just missing a color. You can define an Automatic Formatting rule in your view in Outlook 2003 to color the header text based in the message list based on which category is assigned.
1) View-> Arrange By-> Custom...-> Automatic Formatting...
2) Press Add
3) Name the rule
4) Press Font... to select a font and other font properties
5) Press Condition...
6) Select the More Choices tab
7) Press the Categories... button to select one or more categories that you want to show up in that font setting
8) Press OK
9) Move the rule if needed (the last rule that applies wins when there are conflicting settings)
10) Create additional rules if needed