Red files means they're not being shared. Press the Refresh button (shouldn't do this very often but only if necessary!)

If the incomplete files are in red then that's different. It means LW has lossed the relationship with the downld source & the file listed in the downld window. Perhaps cancel those in red from the downld window & resume them from the LW Library window incomplete folder. That may help. Also see http://www.gnutellaforums.com/showthread.php?t=60383