Build 7478. Had a folder that somehow was read-only. Click toolbar Admin button. Right-click, select Properties, deselect Read-only checkbox. Click Apply. Gears turn, progress bar appears, when done the Read-only checkbox is gone. But folder is still red, and when right-click and select Properties box is checked again.
Click on toolbar Set Attributes button, turn off Read-only off that way. Folder no longer Read-only.
The Properties dialog is part of Windows, not part of Opus. The R (Read-Only) attribute on folders has a special meaning to the Windows shell, so it may not let you clear it on certain folders, although that's just a guess. (It doesn't mean the folder is read-only; it means things should check for a desktop.ini file inside it which may customize how it looks. Makes no sense, but that's Windows for you!)
Red folders usually means the S (System) attribute is set, not that the R (Read-Only) attribute is. (They're often both set at once.)