Only a check for the interior color of the selected cell has been introduced.
Const BlackInterior = 4210752
If ActiveCell.Interior.Color <> BlackInterior Then
The color value for a black cell (at least the shade of black which you have used) is 4210752.
I have defined a constant named BlackInterior , since it is easier to remember a name like this rather than a value like 4210752.
The code then checks for whether the interior color of the cell where the cursor is placed is this color or not ; only if it is not this color , the buttons Buton and Effacer will work , since this same check has been used in both the macros.