Color.a = fAlpha; applies the Entity.alpha to the output color
with this you can make the entity transparent when decreasing the .alpha value of the entity
This line isn't wrong...
(Colormap alpha isn't supported, yet)
you set Color.a = fAlpha, but you never set fAlpha
fAlpha is passed by the engine to the shader. It contains the entity.alpha value with the range [0-1]
