My image renders in black and white and not on the color it shows on the compositor? I am making a wormhole like portal that opens up shrinks and grows for a bit and then dissipates. In the compositor it shows that it is a dark purple color but when I go to render the animation it comes out as black and white and I have no idea what's causing this. I used a youtube tutorial in case you want to comb through it
( https://www.youtube.com/watch?v=TWNLOjw5HYc ) (I know it says its for shockwaves, but I'm using it for my purposes) 


as you can see when it renders it loses all color. If you also want to see a picture of my node setup just ask and I'll screenshot it.
What you see in the backdrop of the compositor is the output plugged to the active "Viewer" node in compositor, while the final render result is the thing that is plugged into the "Composite" node. From your screenshot it looks like your "Composite" node is not plugged into the end of the node chain, but rather into some node a bit earlier in the chain. Attach it into the same socket your viewer node is plugged into, and you should get the same result you see.