What does a red-colored filename mean?

First you need to know the VT100 color code

http://www.termsys.demon.co.uk/vtansi.htm

I don't know what your text actually looks like, but "red text" is 31.

Then you want to look at the dircolors command, and find everything that has a 31 in it. In my case, that would be:

or=40;31;01
*.tar=01;31
*.tgz=01;31
*.arj=01;31
*.taz=01;31
*.lzh=01;31
*.lzma=01;31
*.tlz=01;31
*.txz=01;31
*.zip=01;31
*.z=01;31
*.Z=01;31
*.dz=01;31
*.gz=01;31
*.lz=01;31
*.xz=01;31
*.bz2=01;31
*.bz=01;31
*.tbz=01;31
*.tbz2=01;31
*.tz=01;31
*.deb=01;31
*.rpm=01;31
*.jar=01;31
*.rar=01;31
*.ace=01;31
*.zoo=01;31
*.cpio=01;31
*.7z=01;31
*.rz=01;31

Then you can go here

http://www.bigsoft.co.uk/blog/index.php/2008/04/11/configuring-ls_colors

which tells you

• or is an "orphan", a symbolic link with no target
• the rest are file globs that match assorted archive and compression schemes

.pem doesn't appear on my list, and .pem files aren't colored on my system, so I can't help you further than that. But I'd guess "orphan".

Most Linux distros by default usually color-code files so you can immediately recognize what type they are.You are right that red means archive file and .pem is an archive file. An archive file is just a file composed of other files. Examples you might be more familiar with might include .zip, .rar, or .tar files.

If you want to know more about .pem files this post has a good explanation