Sounds like you have the STATUS column disabled or overlaid with another column. This column shows empty when the email has been read and contains a small ball-like object when unread. To enable the column, Tools->Options->Mailboxes, and place a check next to Status. Click OK. If the column is already enabled, then a neighboring column might be overlaying it. To fix this, click and grab the small black separator line at the left and look for a small ball column.
Labels are used to assign color to messages of some user determined likeness. For instance, I have a RED label set up looking for alert email messages from root; a BLUE label from co-workers; a GREEN label for family.. You get the picture. You create the labels in Tools->Options->Labels by choosing colors (click on the default color box) and give it a name. Then you assign its association with email by setting up filters. Click Tools->Filters to open the filters dialog box. Click New to create a new filter (or hilite an existing one). You assign a label by setting it in the Action section. In one of the pull down boxes, select "Make Label" to set the label to None. Click on None to choose one of your labels you set up in options. Close the Filters dialog (X in the upper right corner) and save your changes. Next time you get an email with your Match specifications, the line will appear in your chosen label color.
Hope this helps! ;-)