When the new Invisible radio button is selected, I set the alpha value of the color to 0, and I use this nul alpha to hide some parts in 3D. As all color values in Sweet Home 3D were set with an alpha equal to 0xFF, I didn't think this way of doing could cause any side effect, except you probably handled colors differently. [:(]
That could explain some reports I received about items becoming invisible when a white color is set. Would that wrong color come from a setting of your plugin?