Render layer confusion I'm trying to composite a shockwave effect with the blender render engine.
My scene is currently set up with two render layers:  

Layer one: Text, two lamps and a camera.
Layer two: shockwave.

I have two issues currently, however I think the first issue may be beyond the scope of this question, I'm not entirely sure if it's something to do with the layer comp.

Issue One: The shockwave colouring seems not to be working from certain frames. Even though nothing is keyframed, everything seems to desaturate from frame 40 to about frame 100. 

Issue Two: The final render is rendering the shockwave layer in front of the text when the object is behind the text. If I switch the alpha mix over node's inputs none of the actual shockwave renders, only the text layer.

Download the Blend
Ok, there are a number of issues with your file:


Select Layers 1 and 2 in the viewport to have both layers render.





In the Render>Shading panel you should select Transparent instead of Sky for the Alpha setting. This will allow your Text layer to render with an alpha channel instead of black.





Secondly, your Hue/Sat compositing node affecting the Shockwave layer IS keyframed on the Value field. Try muting it to see the difference.





Reverse the inputs on your Alpha Over node to put the shockwave behind.






The shockwave image is very light when viewing in Color+Alpha mode in the UV/Image Editor. If you switch to Color only you can see a stronger effect. Alternatively, you could composite a black background behind everything to see it better.