I have found what seems to be a bug with renderer.Fill when i used a fill for a plugin where i wanted a simple visual placeholder.
With the Edittime if you have a plugin where you have this -
IDEInstance.prototype.Draw = function(renderer)
renderer.Fill(this.instance.GetBoundingQuad(), cr.RGB(100, 100, 255)) // Currently has a bug
If you have that in the plugin and then start a new project and add the plugin you see the blue fill working correctly. However if you create a sprite with a image then add other copies of the plugin with this it will then use the texture from the sprite mixing it with the fill color.
So it seems for some reason it is getting sent the texture from other quads even when something is not using them.
I did some testing with other things and Outline and Line seem to do a very similar thing where they appear darker. Outline also has another bug where it seems to have a pixel missing on the lower left side.
I have a request also, it would be useful to have a extra , available for renderer.Fill etc to set a alpha value. I can't seem to find a way to set a alpha value for them so i think that would be a nice solution.