LaurentGomila/SFML — comment on commit 017ef652f98d20847b0c87076558ae0c5db50e25
File:  line 0
By retep998:

When an sf::Texture is removed, then attempting to use the texture will simply result in OpenGL not binding any texture at all. Thus when you try to draw a sprite, or use a texture, there will be no texture bound so the color of the pixels will be whatever color you're currently drawing with, which is white by default. This has nothing to do with the Resource system, and is simply the way OpenGL works by default.
So yes, you will still have that default of white after removing an sf::Texture.