I just woke up so a little slow in understanding. lol
incomplete files will be red in the incomplete folder 'if' you have partial file sharing turned off. Even if you enable this, only new incomplete downloads will be colored black.
Another reason they can be red is if LW no longer recognises them. This might be due to LW making a duplicate which it is or did use for the downloading file.
* Another reason might be the days you have it set to keep incomplete files. Check under Tools -> Options -> Saving. This setting is unavailable in LW 5 from memory. If their use-by date has been past, then LW 'might' have wiped all record from them in it's downloading history preferences. (I have mine set to 9999 days.)
I presume you have tried Resume from the Library window. If they are already listed in the downloads window then this will not have a major effect. But in cases where LW refuses to load incomplete files into the download window, they need to be resumed from incomplete window; in this scenario, they will all show zero % downloaded until the files actually start to download again where their previous download % will show.
Now for a general statement about incomplete files. Some people only come onto the network once a week or less. So you may end up with having incomplete files for many months as you await those people being online or hoping there are alternate sources (other people sharing identically hashed file.) Continual searches, using Get More Sources & coming online at different times consistently may eventually help such files to download.
I guess it depends on whether there are alternates for the files or not. Sometimes finding an alternate, then if that downloads, cancel the one you were unable to download & remove that incomplete file from the incomplete folder.
OH .. you can right-click the heading-bars (column headings) & choose to show more options. This is available in all windows. Choose to show Extended Tooltips. Then hover your cursor over the files. This will give you some information about each file (eg: when it was started, how many KB's downloaded, whether any data is corrupted, etc.)