If I understood you correctly you're trying to upload the black skin; but LFSW won't let you upload it and shows you the gold skin (saying a skin with the same name is already in use).
Best would be the rename your skin (give it a unique name - i.e. VWS_FSP_satellite_1.jpg) and then upload it.
Rename the "black" skin that you have in your lfs/data/skins folder to the name that you uploaded with (i.e. VWS_FSP_satellite_1.jpg).
Now when you go to pits, set the car, click on new colors and then select the renamed-skin from the list, i.e. FSP_satellite_1 and use it. When you leave pits, others will see the skin you just uploaded to LFSW.
It sounds a bit complicated because of the skin renaming thing, but basically all you have to do is give the skin a unique name and then upload it.