You are adding green to black. It doesn't get greener than green that way. The benchmark adds colored dots to a none-black background, which makes it look more intense. Try to use a texture that has a color fading towards the edges and maybe don't use 10 as a setting for the transparency, because that makes the fading almost opaque. Try 0..3 instead. It won't be any brighter, but it might look more like you want it to.