By default, the overlay icons displayed under the thumbnail in the Manage Mode are of grayscale mode. Use the right square bracket ( ] ) to toggle among grayscale, color and invisible mode.

The left square bracket ( [ ) controls which overlay icon is going to be colored.

For more information about how to change the File List View in ACDSee, please refer to the ACDSee Help File : Manage Mode > Browsing > Changing Views