After a merge the icons reprensenting folder a has change to this yellow icon representing one parent folder and a child one (With the label Appls beside) :
Anyone has an idea what's the meaning of this icon? All the other folder icon are normal.
The grey icon means that the folder has been converted to a Branch Root and that it (optionally) has a branch relationship with another Branch elsewhere in the repository.
Note: You can convert a folder to a branch using the Convert to Branch option in the Source Control Explorer without directly creating a relationship to another branch.
For more information see the Branch folders and files topic on MSDN.
The yellow "Branched folder" icon is not a standard icon of Visual Studio, but a feature if the TFS Source Control Explorer Extensions from the Visual Studio Gallery.
With the File Icon change option off:
Wit the File Icon change option on:
From the extension gallery description:
File icon change
In the file list on the left side of Source Control Explorer window are branched files displayed with changed icon.
Icon is displayed at files that are target of Branch operation or if file is branched only to one location. If file is branched to more than one location its icon is changed to icon .