Files are compressed when they have not been used for a while (I don't know how long), but they may still be needed for the apps they belong to. Don't just haphazardly delete them.
They won't ordinarily be deleted by Disk Cleanup, either, since they are not temp files without any further use.
If you have compression turned off, your files are the color you want, then I'd say you're finished and to leave the rest alone.
How did they get compressed in the first place? Good question. I could have sworn that I turned off compression the last time I installed, but I had compressed files anyway. Decided that it was a mystery not worth probing.